RFR: 8298469: Obsolete legacy parallel class loading workaround for non-parallel-capable class loaders [v2]

[Coleen Phillimore]

> This change removes the JVM code and option (default off) to synchronize class loading for non-parallel capable class loading.  For more information see: https://bugs.openjdk.org/browse/JDK-8295673
> and Release Note for the option in 20: https://bugs.openjdk.org/browse/JDK-8296446
> 
> Now Release Note for removal: https://bugs.openjdk.org/browse/JDK-8303967
> 
> Tested with tier1-7.

Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:

  Fix comments.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/12974/files
  - new: https://git.openjdk.org/jdk/pull/12974/files/80d6aff0..14f56319

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12974&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12974&range=00-01

  Stats: 2 lines in 1 file changed: 1 ins; 1 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/12974.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12974/head:pull/12974

PR: https://git.openjdk.org/jdk/pull/12974