RFR: 8260605: Various java.lang.invoke cleanups [v5]

[Claes Redestad]

> - Remove unused code
> - Inline and simplify the bootstrap method invocation code (remove pointless reboxing checks etc)
> - Apply pattern matching to make some code more readable

Claes Redestad 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 seven additional commits since the last revision:

 - Revert pattern matching changes covered by #2913
 - Merge branch 'master' into invoke_cleanup
 - Missing .values
 - More cleanup, reduce allocations in InvokerBytecodeGenerator
 - Missing outstanding changes
 - Avoid unnecessary reboxing checks, inline and simplify class/mt invokes
 - j.l.invoke cleanups

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/2300/files
  - new: https://git.openjdk.java.net/jdk/pull/2300/files/0e3768b8..b20073e3

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2300&range=04
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2300&range=03-04

  Stats: 93145 lines in 2437 files changed: 48324 ins; 24814 del; 20007 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2300.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2300/head:pull/2300

PR: https://git.openjdk.java.net/jdk/pull/2300