RFR: 8321139: jlink's man page does not document the --compress option correctly [v5]

[Ana Maria Mihalceanu]

> This PR looks into aligning the behavior and documentation for `--compress` option and plugin of `jlink`:
> 
> - When an user provides `-c {0|1|2}` to `jlink`, then the tool should process it as when receiving `--compress={0|1|2}`. As these values are now deprecated, a warning should be issued to the end user.
> - When an user provides `-c zip-[0-9]` to `jlink`, then the tool should process it as when receiving `--compress=zip-[0-9]`.
> - When no compression level is given, meaning the `jlink` command does not contain either `-c` or `--compress` with a value, the default level selected is `zip-6`.
> - The `--compress` option description reflects above behavior and warns that previous compression levels are deprecated to be removed in a future release.
> - The `--plugin` option description reflects the implementation behavior and warns that previous compression levels are deprecated to be removed in a future release.
> 
> Some implementation details and choices:
> - While current `jlink` man page states that the tool supports `-c={0|1|2}`, I inspired myself on how `javac` supports the shortened options https://docs.oracle.com/en/java/javase/25/docs/specs/man/javac.html#options.
> - While `-c 0` and `--compress=0` produce the same compression level as of `zip-0`, I preferred not to tie the new compression level to the old value for the option. I believe that this approach would make it easier/cleaner to remove the code for the deprecated values (when their time comes).
> - While `-c 2` and `--compress=2` produce the same compression level as of `zip-6`, I preferred not to tie the new compression level to the old value for the option. I believe that this approach would make it easier/cleaner to remove the code for the deprecated values (when their time comes).
> - As I didn't affect the actual compression implementation, only the options, I tested only how the options are mapped. The actual set and validation of the options was not affected, hence I didn't change those tests.

Ana Maria Mihalceanu has updated the pull request incrementally with one additional commit since the last revision:

  Refactor variable name.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/28359/files
  - new: https://git.openjdk.org/jdk/pull/28359/files/fccce74b..82f4e8d1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28359&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28359&range=03-04

  Stats: 6 lines in 1 file changed: 0 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/28359.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28359/head:pull/28359

PR: https://git.openjdk.org/jdk/pull/28359