Added shared prefetch counter

[shubhamsrkdev]

Problem

Across clone and slices of MemorySegmentIndexInput the consecutivePrefetchHitCount was getting reset leading to repeated calls.

Solution

Added a shared prefetch counter, through reference - this should maintain count through clones and slices.

Fixes #15571

The benchmarks are looking good :

                            TaskQPS baseline      StdDevQPS my_modified_version      StdDev                Pct diff p-value
                          IntSet      814.31      (4.5%)      794.78      (6.2%)   -2.4% ( -12% -    8%) 0.159
                      TermDTSort      248.72      (5.8%)      245.11      (7.0%)   -1.5% ( -13% -   12%) 0.476
                 LowSloppyPhrase       38.85      (3.9%)       38.37      (4.7%)   -1.3% (  -9% -    7%) 0.360
            BrowseDateSSDVFacets        0.90      (8.4%)        0.89      (9.0%)   -0.8% ( -16% -   18%) 0.767
                 MedSloppyPhrase       45.58      (3.0%)       45.22      (3.4%)   -0.8% (  -6% -    5%) 0.445
                HighSloppyPhrase       12.27      (6.0%)       12.20      (5.9%)   -0.6% ( -11% -   12%) 0.749
                          IntNRQ      295.84      (1.7%)      294.19      (1.7%)   -0.6% (  -3% -    2%) 0.302
                         Respell       45.97      (2.5%)       45.77      (1.9%)   -0.4% (  -4% -    4%) 0.539
           BrowseMonthTaxoFacets        2.78      (2.0%)        2.77      (0.9%)   -0.4% (  -3% -    2%) 0.455
                    HighSpanNear       27.73      (1.5%)       27.63      (1.4%)   -0.3% (  -3% -    2%) 0.471
                          Fuzzy2       68.17      (2.6%)       67.95      (2.1%)   -0.3% (  -4% -    4%) 0.668
            HighIntervalsOrdered       32.46      (8.2%)       32.42      (9.3%)   -0.1% ( -16% -   18%) 0.965
                           range     3603.08      (4.7%)     3600.78      (4.9%)   -0.1% (  -9% -    9%) 0.966
     BrowseRandomLabelSSDVFacets        3.22      (8.7%)        3.22      (8.1%)   -0.0% ( -15% -   18%) 0.996
          OrHighMedDayTaxoFacets        4.69      (1.9%)        4.69      (1.9%)    0.0% (  -3% -    3%) 0.975
           HighTermDayOfYearSort      365.33      (1.4%)      365.41      (1.2%)    0.0% (  -2% -    2%) 0.959
                          Fuzzy1       70.44      (2.4%)       70.48      (1.8%)    0.1% (  -4% -    4%) 0.940
                        PKLookup      197.00      (1.7%)      197.17      (2.2%)    0.1% (  -3% -    4%) 0.893
     BrowseRandomLabelTaxoFacets        2.39      (1.9%)        2.39      (2.0%)    0.2% (  -3% -    4%) 0.753
            HighTermTitleBDVSort       63.91      (1.2%)       64.09      (1.0%)    0.3% (  -1% -    2%) 0.427
           BrowseMonthSSDVFacets        4.52      (6.4%)        4.53      (7.2%)    0.3% ( -12% -   14%) 0.883
       BrowseDayOfYearSSDVFacets        4.52      (8.1%)        4.53      (7.7%)    0.4% ( -14% -   17%) 0.888
             MedIntervalsOrdered       61.93      (4.5%)       62.17      (5.3%)    0.4% (  -9% -   10%) 0.811
                     MedSpanNear      149.61      (1.3%)      150.36      (1.0%)    0.5% (  -1% -    2%) 0.167
                     LowSpanNear      102.70      (1.2%)      103.25      (0.8%)    0.5% (  -1% -    2%) 0.099
         AndHighMedDayTaxoFacets       71.17      (0.8%)       71.56      (0.9%)    0.5% (  -1% -    2%) 0.053
             LowIntervalsOrdered      273.02      (3.2%)      274.68      (4.2%)    0.6% (  -6% -    8%) 0.608
                       LowPhrase       54.15      (2.4%)       54.48      (1.7%)    0.6% (  -3% -    4%) 0.349
        AndHighHighDayTaxoFacets       35.01      (0.9%)       35.28      (0.9%)    0.8% (  -1% -    2%) 0.006
            MedTermDayTaxoFacets       35.19      (1.2%)       35.51      (0.8%)    0.9% (  -1% -    2%) 0.003
       BrowseDayOfYearTaxoFacets        3.12      (4.1%)        3.15      (4.6%)    1.0% (  -7% -   10%) 0.480
            BrowseDateTaxoFacets        3.10      (4.1%)        3.13      (4.7%)    1.0% (  -7% -   10%) 0.456
                      HighPhrase       87.16      (2.9%)       88.09      (1.9%)    1.1% (  -3% -    6%) 0.176
                     AndHighHigh      261.20      (2.9%)      266.49      (2.8%)    2.0% (  -3% -    7%) 0.025
                       MedPhrase      256.22      (1.8%)      261.49      (1.5%)    2.1% (  -1% -    5%) 0.000
               HighTermMonthSort     1355.00      (2.3%)     1386.97      (3.3%)    2.4% (  -3% -    8%) 0.009
                    OrNotHighMed      585.83      (3.3%)      603.68      (3.9%)    3.0% (  -4% -   10%) 0.008
                      OrHighHigh      309.70      (5.2%)      319.44      (3.8%)    3.1% (  -5% -   12%) 0.029
                        Wildcard      815.29      (3.2%)      845.21      (2.9%)    3.7% (  -2% -   10%) 0.000
                       OrHighMed      626.92      (3.0%)      654.05      (2.1%)    4.3% (   0% -    9%) 0.000
               HighTermTitleSort      149.65      (2.8%)      156.38      (4.8%)    4.5% (  -3% -   12%) 0.000
                         MedTerm     1168.83      (4.1%)     1222.83      (5.0%)    4.6% (  -4% -   14%) 0.001
                   OrHighNotHigh      728.82      (3.9%)      762.67      (4.1%)    4.6% (  -3% -   13%) 0.000
                   OrNotHighHigh      867.08      (2.8%)      907.92      (3.7%)    4.7% (  -1% -   11%) 0.000
                        HighTerm      734.14      (5.8%)      769.02      (5.5%)    4.8% (  -6% -   16%) 0.008
                    OrHighNotMed      858.31      (3.1%)      901.62      (3.4%)    5.0% (  -1% -   11%) 0.000
                      AndHighMed      573.81      (2.6%)      603.39      (1.6%)    5.2% (   0% -    9%) 0.000
                    OrNotHighLow     1102.50      (2.7%)     1165.73      (2.8%)    5.7% (   0% -   11%) 0.000
                         LowTerm     1691.06      (3.5%)     1822.95      (3.7%)    7.8% (   0% -   15%) 0.000
                       OrHighLow     1074.51      (2.6%)     1159.81      (2.5%)    7.9% (   2% -   13%) 0.000
                    OrHighNotLow     1076.27      (4.0%)     1167.56      (5.4%)    8.5% (   0% -   18%) 0.000
                      AndHighLow     1250.35      (2.1%)     1374.26      (3.3%)    9.9% (   4% -   15%) 0.000
                         Prefix3      742.64     (16.9%)      861.01     (20.1%)   15.9% ( -18% -   63%) 0.007