RFR: 8337839: Make a few fields in MergeCollation static

[Andrey Turbanov]

3 fields in java.text.MergeCollation could be made 'static':
1. BITARRAYMASK
2. BYTEPOWER
3. BYTEMASK

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Commit messages:
 - [PATCH] Make a few fields in MergeCollation static

Changes: https://git.openjdk.org/jdk/pull/20323/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20323&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8337839
  Stats: 4 lines in 1 file changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/20323.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20323/head:pull/20323

PR: https://git.openjdk.org/jdk/pull/20323