Fix the problem that the first frame of pointer's deltaPosition is incorrect

[cptbtptpbcptdtptp]

Need to assign a value to the Position when initializing a Pointer.

[codecov]

Codecov Report

Patch coverage: 91.42% and project coverage change: -0.81% ⚠️

Comparison is base (5d7d8dc) 61.91% compared to head (d761367) 61.10%.

❗ Current head d761367 differs from pull request most recent head df3eb82. Consider uploading reports for the commit df3eb82 to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           dev/1.1    #1749      +/-   ##
===========================================
- Coverage    61.91%   61.10%   -0.81%     
===========================================
  Files          464      464              
  Lines        20935    20926       -9     
  Branches      3386     3382       -4     
===========================================
- Hits         12961    12786     -175     
- Misses        6777     6956     +179     
+ Partials      1197     1184      -13     

Files Changed	Coverage Δ
packages/core/src/input/pointer/PointerManager.ts	91.90% <91.42%> (+2.89%)	⬆️

... and 17 files with indirect coverage changes

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