RFR: 8332745: Method::is_vanilla_constructor is never used

[Dan Heidinga]

Removed dead code related to identifying empty constructors.  Missed when [JDK-8057777](https://bugs.openjdk.org/browse/JDK-8057777) cleaned up JVM_AllocateNewObject.

Passes mach5 tier1.

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Commit messages:
 - Merge remote-tracking branch 'upstream/master' into 8332745
 - 8332745: Method::is_vanilla_constructor is never used

Changes: https://git.openjdk.org/jdk/pull/19367/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19367&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8332745
  Stats: 78 lines in 5 files changed: 0 ins; 76 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/19367.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19367/head:pull/19367

PR: https://git.openjdk.org/jdk/pull/19367