RFR: 8323546: Clarify docs for Compiler.perfmap filename parameter, and other misc related jcmd doc cleanups [v4]

[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 incrementally with one additional commit since the last revision:

  fix default filename issue

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/17359/files
  - new: https://git.openjdk.org/jdk/pull/17359/files/16f23147..ba64b6f2

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17359&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17359&range=02-03

  Stats: 16 lines in 1 file changed: 12 ins; 0 del; 4 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