RFR: 8323546: Clarify docs for Compiler.perfmap filename parameter, and other misc related jcmd doc cleanups [v3]

[Chris Plummer]

> The jcmd docs for Compiler.perfmap currently say:
> 
>     - *filename*: (Optional) The name of the map file (STRING, no default value)
> 
> However, there is a default, so not only should that be made more clear in the above, but also some descriptive text as to how the default is generated should be added.
> 
> VM.cds has a similar issue, but already has the descriptive text, so just the "no default value" part needs to be fixed.
> 
> Another change needed is to consistently use *filename* (italics) instead of `filename` (monospace). Note this is how html formatting is done. For the man page formatting, *filename* does no formatting and `filename` is displayed in color if supported. Personally I prefer `filename`, but it seems that there is already a strong precedence for using italics in the *arguments* list. For example:
> 
>     *arguments*:
> 
>     - *flag name*: The name of the flag that you want to set (STRING, no
>         default value)
> 
>     - *string value*: (Optional) The value that you want to set (STRING, no
>         default value)

Chris Plummer has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - Merge branch 'master' into 8323546_jcmd_doc
   merge
 - update jcmd help output to include default filename
 - minor improvements related to Compiler.perfmap filename argument

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/17359/files
  - new: https://git.openjdk.org/jdk/pull/17359/files/b6819c77..16f23147

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17359&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17359&range=01-02

  Stats: 3946 lines in 88 files changed: 2665 ins; 801 del; 480 mod
  Patch: https://git.openjdk.org/jdk/pull/17359.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17359/head:pull/17359

PR: https://git.openjdk.org/jdk/pull/17359