RFR: 8342967: Lambda deduplication fails with non-metafactory BSMs and mismatched local variables names [v5]

[Aggelos Biboudis]

> After experimentation and under certain conditions, a few equivalent lambdas (up to variable renaming) fail to deduplicate.
> 
> `TreeHasher` and `TreeDiffer` are now aware that other bootstraps may appear in lambda bodies (e.g. `SwitchBootstraps.typeSwitch`) and that variable names do not matter (when they appear in method/lambda definitions). In the first case equivalence is checked based on `bsmKey` and not the `Dynamic{Var, Method}Symbol` itself.
> 
> The test was also adjusted since it was assuming BSM with certain structure only (that `.get(1)` was unprotected).

Aggelos Biboudis has updated the pull request incrementally with one additional commit since the last revision:

  Refactor deduplication test
  
  - introduce two kinds of groups
  - extract assertNotEqualsWithinGroup
  - extract isMethodWithName
  - extract addToGroup

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Changes:
  - all: https://git.openjdk.org/jdk/pull/21687/files
  - new: https://git.openjdk.org/jdk/pull/21687/files/afed3649..1c80a7c4

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21687&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21687&range=03-04

  Stats: 111 lines in 3 files changed: 35 ins; 10 del; 66 mod
  Patch: https://git.openjdk.org/jdk/pull/21687.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21687/head:pull/21687

PR: https://git.openjdk.org/jdk/pull/21687