RFR: JDK-8283140: Remove unused encoding classes/operands from x86_64.ad [v7]

[Cesar Soares Lucas]

> These encoding classes became dead code when the instructions' definitions were patched to use the MacroAssembler.
> 
> Tested with tier 1-3 on Linux, Windows & MacOS.

Cesar Soares Lucas has updated the pull request incrementally with one additional commit since the last revision:

  Add 'mark' back.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/16319/files
  - new: https://git.openjdk.org/jdk/pull/16319/files/8e64c93e..b49aa52d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16319&range=06
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16319&range=05-06

  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/16319.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16319/head:pull/16319

PR: https://git.openjdk.org/jdk/pull/16319