RFR: 8327651: Rename DictionaryEntry members related to protection domain [v2]

[Ioi Lam]

> Rename `DictionaryEntry::_pd_set` to `_package_access_cache`, and rename all related methods accordingly.
> 
> The old name was very confusing. It makes one wonder,
> 
>> Is `DictionaryEntry::_pd_set` related to the `java.lang.Class.getProtectionDomain()` of the `DictionaryEntry::_instance_klass` in any way?
> 
> (Hint, they have absolutely no relationship to each other).
> 
> I am making this PR as future changes in the Leyden project may be touching this area. I don't want the reviewers of my future PRs be confused by this code.
> 
> ----------------
> This PR is mostly name changes and comment clarification.
> 
> Other than a log message change for clarification, there are no behavioral changes in this PR.

Ioi Lam has updated the pull request incrementally with one additional commit since the last revision:

  @coleenp review -- add comments about avoiding Java upcalls

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/18222/files
  - new: https://git.openjdk.org/jdk/pull/18222/files/757c7953..b0ca86d1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18222&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18222&range=00-01

  Stats: 7 lines in 1 file changed: 6 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/18222.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18222/head:pull/18222

PR: https://git.openjdk.org/jdk/pull/18222