feature: test where function

feature: add parser.

…ect/tidb into feature-add-udf-support

* 'feature-add-udf-support' of https://github.com/JustProject/tidb: (26 commits)
  *: fix bug that the kill command doesn't work when the killed session is waiting for the pessimistic lock (pingcap#12852)
  executor: fix the projection upon the indexLookUp in indexLookUpJoin can't get result. (pingcap#12889)
  planner, executor: support create view on union (pingcap#12595)
  planner/cascades: introduce TransformationID in cascades planner (pingcap#12879)
  executor: fix data race in test (pingcap#12910)
  executor: reuse chunk row for insert on duplicate update (pingcap#12847)
  ddl: speed up tests (pingcap#12888)
  executor: speed up test (pingcap#12896)
  expression: implement vectorized evaluation for `builtinSecondSig` (pingcap#12886)
  expression: implement vectorized evaluation for `builtinJSONObjectSig` (pingcap#12663)
  expression: speed up builtinRepeatSig by using MergeNulls (pingcap#12674)
  expression: speed up unit tests under the expression package (pingcap#12887)
  store,kv: snapshot doesn't cache the non-exists kv entries lead to poor 'insert ignore' performance (pingcap#12872)
  executor: fix data race in `GetDirtyTable()` (pingcap#12767)
  domain: increase TTL to reduce the occurrence of reporting min startTS errors (pingcap#12578)
  executor: split test for speed up (pingcap#12881)
  executor: fix inconsistent of grants privileges with MySQL when executing `grant all on ...` (pingcap#12330)
  expression: implement vectorized evaluation for `builtinJSONUnquoteSig` (pingcap#12841)
  tune grpc connection count between tidb and tikv (pingcap#12884)
  Makefile: change test parallel to 8 (pingcap#12885)
  ...