RFR: 8344056: Use markdown format for man pages

[Christian Stein]

On Wed, 13 Nov 2024 17:05:25 GMT, Magnus Ihse Bursie <ihse at openjdk.org> wrote:

> 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.

A missing `.1` to `.md` file extension change in `javadoc`'s manpage self-test `CheckManPageOptions.java` is causing the CI to fail.

Details in https://github.com/openjdk/jdk/pull/22081#issuecomment-2474760888

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Changes requested by cstein (Committer).

PR Review: https://git.openjdk.org/jdk/pull/22081#pullrequestreview-2434491865