RFR: 8344079: Minor fixes and cleanups to compiler lint-related code [v6]

[Archie Cobbs]

> Please review these changes with some minor lint-related fixes and cleanups.
> 
> See [JDK-8344079](https://bugs.openjdk.org/browse/JDK-8344079) for a more detailed description.

Archie Cobbs has updated the pull request incrementally with two additional commits since the last revision:

 - Refactor to clarify handling of special flag "-XDwarnOnAccessToMembers".
 - Tighten up declared type of lexWarning() parameter.

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/22056/files
  - new: https://git.openjdk.org/jdk/pull/22056/files/d0d25725..c2f770b5

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=22056&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=22056&range=04-05

  Stats: 25 lines in 3 files changed: 19 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/22056.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22056/head:pull/22056

PR: https://git.openjdk.org/jdk/pull/22056