RFR: 8280543: Update the "java" and "jcmd" tool specification for CDS

[Ioi Lam]

The discussion of CDS in the man pages need to be cleaned up and updated to match the latest functionalities and intended usage. 

For java.md:

- Reorganized the flow of the doc: Overview -> How to use -> How to create -> Restrictions and notes. I think this will be easier to read.
- Added information about `jcmd VM.cds static_dump|dynamic_dump`
- Removed a few sections that are no longer relevant or are uncommon usage (config files, sharing across two different apps)
- Removed discussion of uncommon error conditions (such as array classes)
- Removed detailed error messages. I think a simple note like "unsupported" will be good enough for readers of the man page.
- Removed discussion of different version of JDK (these should have been in release note)

For jcmd.md:

- Added some more details about default file name and output directory.

For ease of reviewing, please see the pre-rendered HTML pages:

http://cr.openjdk.java.net/~iklam/jdk19/8280543-update-java-and-jcmd-manpage-for-cds2/specs/man/

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Commit messages:
 - 8280543: Update the "java" and "jcmd" tool specification for CDS

Changes: https://git.openjdk.java.net/jdk/pull/7255/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7255&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8280543
  Stats: 508 lines in 2 files changed: 35 ins; 364 del; 109 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7255.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7255/head:pull/7255

PR: https://git.openjdk.java.net/jdk/pull/7255