RFR: 8356202: Cleanup Source code in String Implementation Classes [v4]

[Roger Riggs]

> Code cleanup in java.lang.StringLatin1 and StringUTF16.
> Remove the `public` qualifier from methods where it is not needed.
> Remove an unused toBytes method.
> Remove unused codePointXXX methods.
> Remove unnecessary casts of primitive types.
> 
> Some of these are suggested by IntelliJ, if the advice should not be taken, I'll revert and update the IDE settings.

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

  Fix indentation on method declarations

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Changes:
  - all: https://git.openjdk.org/jdk/pull/27609/files
  - new: https://git.openjdk.org/jdk/pull/27609/files/13b00f15..5c8b1827

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27609&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27609&range=02-03

  Stats: 10 lines in 2 files changed: 0 ins; 0 del; 10 mod
  Patch: https://git.openjdk.org/jdk/pull/27609.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27609/head:pull/27609

PR: https://git.openjdk.org/jdk/pull/27609