RFR: 8273300: Check Mutex ranking during a safepoint [v6]

[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.

Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:

  Remove safepoint conditional from other assert. The locks should now be in decreasing order.

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5467/files
  - new: https://git.openjdk.java.net/jdk/pull/5467/files/eec9b842..ee2ba0fb

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5467&range=05
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5467&range=04-05

  Stats: 8 lines in 1 file changed: 0 ins; 2 del; 6 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