RFR: 8319778: Remove unreachable code in ObjectSynchronizer::exit [v4]

[Axel Boldt-Christmas]

> In `ObjectSynchronizer::exit` when unlocking on an inflated monitor with `LM_LIGHTWEIGHT` there is a check if the owner is anonymous. That branch should never be take and would indicate that something is wrong with either `ObjectSynchronizer::inflate` or that `ObjectSynchronizer::exit` is trying to unlock a monitor not owned by the `current` thread.
> 
> Changes this to an assert instead. Did not condition the assert on `LM_LIGHTWEIGHT` as this property should hold regardless of locking mode.

Axel Boldt-Christmas 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 four additional commits since the last revision:

 - Merge remote-tracking branch 'upstream_jdk/master' into JDK-8319778
 - Merge remote-tracking branch 'upstream_jdk/master' into JDK-8319778
 - Merge remote-tracking branch 'upstream_jdk/master' into JDK-8319778
 - 8319778: Remove unreachable code in ObjectSynchronizer::exit

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/16602/files
  - new: https://git.openjdk.org/jdk/pull/16602/files/4cf7b701..add233fa

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16602&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16602&range=02-03

  Stats: 6364 lines in 172 files changed: 3596 ins; 822 del; 1946 mod
  Patch: https://git.openjdk.org/jdk/pull/16602.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16602/head:pull/16602

PR: https://git.openjdk.org/jdk/pull/16602