RFR: 8372802: PrintFlagsFinal should also print locked flags

[Frederic Thevenet]

This change aims to provide a way to print all flags including "locked" ones (e.g. Diagnostic and Experimental) without having to explicitly set `+UnlockExperimentalVMOptions` or `+UnlockDiagnosticVMOptions` 

This applies to the following VM options: `PrintFlagsFinal` , `PrintFlagsRanges`, `PrintFlagsInitial`, `PrintFlagsWithComments`, `-XprintFlags`, as well as the `PrintVMFlagsDCmd` diagnostic command (when set to show all flags).

Places that print out only flags that have been changed (i.e. that skip flags with default values), like when during the generation of hs_err reports, are not affected by this.

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Commit messages:
 - Added a jtreg test
 - JDK-8372802: PrintFlagsFinal should also print locked flags

Changes: https://git.openjdk.org/jdk/pull/28579/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28579&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8372802
  Stats: 76 lines in 2 files changed: 75 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/28579.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28579/head:pull/28579

PR: https://git.openjdk.org/jdk/pull/28579