optimize suspend limit into index merge reader as embedded one

[AilinKid]

Enhancement

before

        "SQL": "explain format = 'brief' select /*+ use_index(t, kj) */ * from t where json_contains(j, '[1, 2, 3]') limit 1; -- index merge intersection case, sink limit into table side",
        "Plan": [
          "Limit 1.00 root  offset:0, count:1",
          "└─IndexMerge 0.00 root  type: intersection",
          "  ├─IndexRangeScan(Build) 0.00 cop[tikv] table:t, index:kj(cast(`j` as signed array)) range:[1,1], keep order:false, stats:pseudo",
          "  ├─IndexRangeScan(Build) 0.00 cop[tikv] table:t, index:kj(cast(`j` as signed array)) range:[2,2], keep order:false, stats:pseudo",
          "  ├─IndexRangeScan(Build) 0.00 cop[tikv] table:t, index:kj(cast(`j` as signed array)) range:[3,3], keep order:false, stats:pseudo",
          "  └─Limit(Probe) 0.00 cop[tikv]  offset:0, count:1",
          "    └─TableRowIDScan 0.00 cop[tikv] table:t keep order:false, stats:pseudo"

after

        "SQL": "explain format = 'brief' select /*+ use_index(t, kj) */ * from t where json_contains(j, '[1, 2, 3]') limit 1; -- index merge intersection case, embedding limit into index merge reader",
        "Plan": [
          "IndexMerge 0.00 root  type: intersection, limit embedded(offset:0, count:1)",
          "├─IndexRangeScan(Build) 0.00 cop[tikv] table:t, index:kj(cast(`j` as signed array)) range:[1,1], keep order:false, stats:pseudo",
          "├─IndexRangeScan(Build) 0.00 cop[tikv] table:t, index:kj(cast(`j` as signed array)) range:[2,2], keep order:false, stats:pseudo",
          "├─IndexRangeScan(Build) 0.00 cop[tikv] table:t, index:kj(cast(`j` as signed array)) range:[3,3], keep order:false, stats:pseudo",
          "└─TableRowIDScan(Probe) 0.00 cop[tikv] table:t keep order:false, stats:pseudo"