RFR: 8311943: Cleanup usages of toLowerCase() and toUpperCase() in java.base [v3]

[Glavo]

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

Glavo has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains four commits:

 - Merge remote-tracking branch 'origin/master' into case-conversion-java-base
 - Revert StreamTokenizer.java
 - Update DateTimeFormatterBuilder
 - Avoid locale-sensitive case conversions in java.base

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Changes: https://git.openjdk.org/jdk/pull/14763/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14763&range=02
  Stats: 44 lines in 11 files changed: 6 ins; 0 del; 38 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