RFR: 8253540: InterpreterRuntime::monitorexit should be a JRT_LEAF function

[Coleen Phillimore]

That the monitor has already been unlocked, or is a null stacklock monitor has been already checked in the caller, so
the code that makes it a JRT_ENTRY_NO_ASYNC is unnecessary.

Making it a JRT_LEAF like the compiled method entries makes it safer. We know it can never safepoint and
unintentionally install a async exception.

Tested with tier1-6.

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Commit messages:
 - 8253540: InterpreterRuntime::monitorexit should be a JRT_LEAF function

Changes: https://git.openjdk.java.net/jdk/pull/320/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=320&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8253540
  Stats: 11 lines in 1 file changed: 0 ins; 4 del; 7 mod
  Patch: https://git.openjdk.java.net/jdk/pull/320.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/320/head:pull/320

PR: https://git.openjdk.java.net/jdk/pull/320