RFR: 8369573: Add missing compile commands help documentation for the signature part of method patterns [v3]

[Daniel Lundén]

> The documentation of the signature part of method patterns in `java -XX:CompileCommand=help` is missing. We should add it.
> 
> ### Changeset
> - Improve the documentation of signatures in `java -XX:CompileCommand=help`.
> 
> ### Testing
> 
> - [GitHub Actions](https://github.com/dlunde/jdk/actions/runs/18500483034)
> - `tier1` and HotSpot parts of `tier2` and `tier3` (and additional Oracle-internal testing) on Windows x64, Linux x64, Linux aarch64, macOS x64, and macOS aarch64.

Daniel Lundén has updated the pull request incrementally with one additional commit since the last revision:

  Change from signature to descriptor

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/27818/files
  - new: https://git.openjdk.org/jdk/pull/27818/files/b9ade2d4..9a920ae3

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27818&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27818&range=01-02

  Stats: 6 lines in 1 file changed: 0 ins; 1 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/27818.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27818/head:pull/27818

PR: https://git.openjdk.org/jdk/pull/27818