[code-reflection] RFR: Replace methods "create" in Op subclasses by constructors [v2]

[Mourad Abbay]

> By using flexible constructor bodies feature, we get rid of methods "create" in Op subclasses and we replace it with constructors. We also remove unused constructors and methods in Op subclasses.

Mourad Abbay has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains four commits:

 - Restore constructor and method that have usage
 - Merge branch 'code-reflection' into rm-op-create
   
   # Conflicts:
   #	src/jdk.incubator.code/share/classes/jdk/incubator/code/dialect/core/CoreOp.java
 - Remove unused constructors and methods
 - Replace methods that create Ops from ExternalizedOp, by constructors

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Changes: https://git.openjdk.org/babylon/pull/584/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=584&range=01
  Stats: 90 lines in 2 files changed: 13 ins; 22 del; 55 mod
  Patch: https://git.openjdk.org/babylon/pull/584.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/584/head:pull/584

PR: https://git.openjdk.org/babylon/pull/584