RFR: 8304034: Remove redundant and meaningless comments in opto [v4]

[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 incrementally with two additional commits since the last revision:

 - cleanup more
 - reserve some comments

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/12995/files
  - new: https://git.openjdk.org/jdk/pull/12995/files/309503da..b3fc99e3

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12995&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12995&range=02-03

  Stats: 126 lines in 10 files changed: 5 ins; 121 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/12995.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12995/head:pull/12995

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