RFR: 8304034: Remove redundant and meaningless comments in opto [v7]

[Yi Yang]

> Please help review this trivial change to remove redundant and meaningless comments in `hotspot/share/opto` directory.
> 
> They are either
> 1. Repeat the function name that the function they comment for.
> 2. Makes no sense, e.g. `//----Idealize----` 
> 
> And I think original CC-style code (`if( test )`,`call( arg )`) can be formatted in one go, instead of formatting the near code when someone touches them. But this may form a big patch, and it confuses code blame, so I left this work until we reach a consensus.
> 
> Thanks!

Yi Yang has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains ten commits:

 - Merge branch 'master' into cleanupc2
 - review feedback
 - Merge branch 'master' into cleanupc2
 - restore mistakenly removed lines
 - cleanup more
 - reserve some comments
 - multiple empty lines to one empty lines
 - reserve some comments
 - 8304034: Remove redundant and meaningless comments in opto

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

Changes: https://git.openjdk.org/jdk/pull/12995/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12995&range=06
  Stats: 2759 lines in 117 files changed: 10 ins; 2742 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/12995.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/12995/head:pull/12995

PR: https://git.openjdk.org/jdk/pull/12995