RFR: 8255041: Zero: remove old JSR 292 support leftovers

[Aleksey Shipilev]

JDK-8000780 removed `ZeroInterpreter::method_handle_entry`, but left its helpers around. These have no uses, and can be
eliminated. Attention @rkennke, who did the JDK-8000780 a while ago.

Testing:
 - [x] Linux x86_64 fastdebug zero images
 - [ ] Linux x86_64 release zero bootcycle-images

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Commit messages:
 - 8255041: Zero: remove old JSR 292 support leftovers

Changes: https://git.openjdk.java.net/jdk/pull/758/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=758&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8255041
  Stats: 76 lines in 3 files changed: 0 ins; 76 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/758.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/758/head:pull/758

PR: https://git.openjdk.java.net/jdk/pull/758