RFR: 8349157: Unnecessary Hashtable usage in XKeysym.javaKeycode2KeysymHash

[Andrey Turbanov]

There is a field 'sun.awt.X11.XKeysym#javaKeycode2KeysymHash' which uses legacy Hashtable class.
As this map is read-only and all its content is initialized in '<clinit>' we can safely use immutable Map instead.

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Commit messages:
 - [PATCH] Unnecessary Hashtable usage in XKeysym.javaKeycode2KeysymHash

Changes: https://git.openjdk.org/jdk/pull/23347/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23347&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8349157
  Stats: 20 lines in 1 file changed: 7 ins; 9 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/23347.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23347/head:pull/23347

PR: https://git.openjdk.org/jdk/pull/23347