RFR: JDK-8283140: Remove unused encoding classes/operands from x86_64.ad [v3]

[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:

  Fix typo

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/16319/files
  - new: https://git.openjdk.org/jdk/pull/16319/files/d6199348..e816b9e5

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16319&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16319&range=01-02

  Stats: 3 lines in 1 file changed: 0 ins; 1 del; 2 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