RFR: 8254566: Clarify the spec of ClassLoader::getClassLoadingLock for non-parallel capable loader [v3]

[Mandy Chung]

> The spec of `ClassLoader::getClassLoadingLock` is unclear that this method is intended for parallel-capable class loader implementations to provide an alternate implementation.   For non-parallel-capable class loaders, this method should return this `ClassLoader` object.   The javadoc uses "the default implementation" which could be interpreted that non-parallel-capable class loaders can also override this implementation, which is not the intent.  See https://openjdk.org/groups/core-libs/ClassLoaderProposal.html.

Mandy Chung has updated the pull request incrementally with one additional commit since the last revision:

  make it implSpec per CSR review feedback

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Changes:
  - all: https://git.openjdk.org/jdk/pull/14720/files
  - new: https://git.openjdk.org/jdk/pull/14720/files/e9607f4a..2969ea34

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14720&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14720&range=01-02

  Stats: 2 lines in 1 file changed: 2 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/14720.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14720/head:pull/14720

PR: https://git.openjdk.org/jdk/pull/14720