RFR: 8310502 : optimization for UUID#toString

[温绍锦]

By optimizing the implementation of java.lang.Long#fastUUID, the performance of the java.util.UUID#toString method can be significantly improved.

The following are the test results of JMH: 

Benchmark                     Mode  Cnt      Score      Error   Units
UUIDUtilsBenchmark.new       thrpt    5  92676.550 ±  292.213  ops/ms
UUIDUtilsBenchmark.original  thrpt    5  37040.165 ± 1023.532  ops/ms

-------------

Commit messages:
 - 8310502 : optimization for UUID#toString

Changes: https://git.openjdk.org/jdk/pull/14578/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14578&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8310502
  Stats: 105 lines in 1 file changed: 88 ins; 5 del; 12 mod
  Patch: https://git.openjdk.org/jdk/pull/14578.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14578/head:pull/14578

PR: https://git.openjdk.org/jdk/pull/14578