RFR: 8319822: Use a linear-time algorithm for assert_different_registers()

[Andrew Haley]

At the present time, assert_different_registers() uses an O(N**2) algorithm in assert_different_registers(). We can utilize RegSet to do it in O(N) time. This would be a useful optimization for all builds with assertions enabled.

In addition, it would be useful to be able to static_assert different registers. 

Also, I've taken the opportunity to expand the maximum size of a RegSet to 64 on 64-bit platforms.

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Commit messages:
 - 8319822: Use a linear-time algorithm for assert_different_registers()
 - Better
 - Temp

Changes: https://git.openjdk.org/jdk/pull/16617/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16617&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8319822
  Stats: 63 lines in 2 files changed: 38 ins; 0 del; 25 mod
  Patch: https://git.openjdk.org/jdk/pull/16617.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16617/head:pull/16617

PR: https://git.openjdk.org/jdk/pull/16617