RFR: 8336275: Move common Method and Constructor fields to Executable [v3]

[Chen Liang]

> Move fields common to Method and Field to executable, which simplifies implementation. Removed useless transient modifiers as Method and Field were never serializable.
> 
> Note to core-libs reviewers: Please review the associated CSR on trivial removal of `abstract` modifier as well.

Chen Liang has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains five commits:

 - Fix after merge
 - Merge branch 'master' of https://github.com/openjdk/jdk into feature/executable-inline
 - Merge branch 'master' of https://github.com/openjdk/jdk into feature/executable-inline
 - Redundant transient; Update the comments to be more accurate
 - Inline some common ctor + method fields to executable

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Changes: https://git.openjdk.org/jdk/pull/20188/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20188&range=02
  Stats: 448 lines in 11 files changed: 77 ins; 238 del; 133 mod
  Patch: https://git.openjdk.org/jdk/pull/20188.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20188/head:pull/20188

PR: https://git.openjdk.org/jdk/pull/20188