RFR: 8311943: Cleanup usages of toLowerCase() and toUpperCase() in java.base [v2]

[Glavo]

> Clean up misuses of `toLowerCase()`/`toUpperCase()` in java.base.

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

  Revert StreamTokenizer.java

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Changes:
  - all: https://git.openjdk.org/jdk/pull/14763/files
  - new: https://git.openjdk.org/jdk/pull/14763/files/944acdc4..8b8957f5

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14763&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14763&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/14763.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14763/head:pull/14763

PR: https://git.openjdk.org/jdk/pull/14763