RFR: 8273300: Check Mutex ranking during a safepoint

[Coleen Phillimore]

This change checks lock ranking during a safepoint.  For some reason, safepoint checking was excluded, probably from the days where Safepoint_lock and Threads_lock were used.
Because of checking during a safepoint, some locks had to get lower ranks.  The CR has the details of which locks these were.  The Service_lock complicates things because it's held during oops_do, which may take out other G1 locks.
This was built and tested with Shenandoah.  Thanks to @zhengyu123 for the changes in Shenandoah.
Tests run tier1-8.

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Commit messages:
 - 8273300: Check Mutex ranking during a safepoint

Changes: https://git.openjdk.java.net/jdk/pull/5467/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5467&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8273300
  Stats: 43 lines in 13 files changed: 1 ins; 18 del; 24 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5467.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5467/head:pull/5467

PR: https://git.openjdk.java.net/jdk/pull/5467