[jdk18u] RFR: 8281168: Micro-optimize VarForm.getMemberName for interpreter

[Aleksey Shipilev]

Clean backport to improve interpreter performance.

Additional testing:
 - [x] Linux x86_64 fastdebug `tier1`

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Commit messages:
 - Backport fc77217814eb1a346d7380299abdc2b01a69b4de

Changes: https://git.openjdk.java.net/jdk18u/pull/40/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk18u&pr=40&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8281168
  Stats: 7 lines in 1 file changed: 5 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk18u/pull/40.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk18u pull/40/head:pull/40

PR: https://git.openjdk.java.net/jdk18u/pull/40