RFR: 8370878: C1: Clean up unnecessary ConversionStub constructor [v2]

[Zihao Lin]

> C1: Clean up unnecessary ConversionStub constructor
> Remove class which should not reach.

Zihao Lin has updated the pull request incrementally with one additional commit since the last revision:

  fix arm

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/28096/files
  - new: https://git.openjdk.org/jdk/pull/28096/files/5b4df065..a73b5282

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28096&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28096&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/28096.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28096/head:pull/28096

PR: https://git.openjdk.org/jdk/pull/28096