RFR: 8367129: Move input validation checks to Java for java.lang.StringLatin1 intrinsics [v4]

[Volkan Yazici]

> Moves input validation checks to Java for `java.lang.StringLatin1` intrinsics. While doing so, affected `java.lang.StringUTF16` methods needed to be updated due to relaxed checks at intrinsics. The javadocs of the touched methods are extensively overhauled.

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

  More `indexOf` et al. guards and other review feedback

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Changes:
  - all: https://git.openjdk.org/jdk/pull/28832/files
  - new: https://git.openjdk.org/jdk/pull/28832/files/9bb6cdee..7efdc944

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28832&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28832&range=02-03

  Stats: 44 lines in 2 files changed: 30 ins; 6 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/28832.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28832/head:pull/28832

PR: https://git.openjdk.org/jdk/pull/28832