RFR: 8344056: Use markdown format for man pages [v4]

[Magnus Ihse Bursie]

> Currently, the man pages are stored as troff (a text format) in the open repo, and a content-wise identical copy is stored as markdown (another text format) in the closed repo.
> 
> Since markdown is preferred to troff in terms of editing, we make changes to the man pages in markdown and then convert it to troff.
> 
> This closed-markdown to open-troff processing needs to be done manually by an Oracle engineer. This is done regularly at the start and end of a new release cycle, adding to the burden of creating a new release. It is also done (if any of the reviewers knows about the process) whenever an Oracle engineer updates a man page. If a community contributor changes the behavior of a tool, an Oracle engineer needs to change the documentation for them, since they cannot do it themselves.

Magnus Ihse Bursie has updated the pull request incrementally with one additional commit since the last revision:

  It's somewhat nicer to use \\s instead of space character in regex

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Changes:
  - all: https://git.openjdk.org/jdk/pull/22081/files
  - new: https://git.openjdk.org/jdk/pull/22081/files/dbef493e..7cba61b5

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=22081&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=22081&range=02-03

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/22081.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22081/head:pull/22081

PR: https://git.openjdk.org/jdk/pull/22081