RFR: 8305582: Compiler crash when compiling record patterns with var [v4]

[Aggelos Biboudis]

> While `var` is not allowed in record pattern position the compiler was not checking it. This PR address this issue, by introducing the relevant error symbols and error types.
> 
> e.g., `if (o instanceof ColoredPoint(var(var x, var y), var c)) { }`

Aggelos Biboudis has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains five additional commits since the last revision:

 - Introduce check in Flow
 - Merge branch 'master' into fix-#8305582
 - Update output for DeconstructionpatternsNonVar example
 - Add more tests
 - 8305582: Compiler crash when compiling record patterns with var

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/13331/files
  - new: https://git.openjdk.org/jdk/pull/13331/files/be22af97..cb399ea8

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13331&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13331&range=02-03

  Stats: 7385 lines in 198 files changed: 4251 ins; 2721 del; 413 mod
  Patch: https://git.openjdk.org/jdk/pull/13331.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13331/head:pull/13331

PR: https://git.openjdk.org/jdk/pull/13331