RFR: JDK-8283140: Remove unused encoding classes/operands from x86_64.ad [v6]

[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 two additional commits since the last revision:

 - Update src/hotspot/cpu/x86/x86_64.ad
   
   Co-authored-by: Dean Long <17332032+dean-long at users.noreply.github.com>
 - Update src/hotspot/cpu/x86/x86_64.ad
   
   Co-authored-by: Dean Long <17332032+dean-long at users.noreply.github.com>

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/16319/files
  - new: https://git.openjdk.org/jdk/pull/16319/files/d34e4709..8e64c93e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16319&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16319&range=04-05

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