RFR: 8258588: MD5 MessageDigest in java.util.UUID should be cached [v2]

[PROgrm_JARvis]

> Please review this change moving lookup of MD5 digest in `java.lang.UUID` to an internal holder class.

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

  8258588: add missing " UUIDs" to comment of UUID$Md5Digest

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1821/files
  - new: https://git.openjdk.java.net/jdk/pull/1821/files/73eb2c4f..37db4c56

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1821&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1821&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1821.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1821/head:pull/1821

PR: https://git.openjdk.java.net/jdk/pull/1821