RFR: 8343110: Add getChars(int, int, char[], int) to CharSequence and CharBuffer [v12]

[Markus KARG]

> This Pull Request proposes an implementation for [JDK-8343110](https://bugs.openjdk.org/browse/JDK-8343110): Adding the new method `public void getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)` to the `CharSequence` interface, providing a **bulk-read** facility including a default implementation iterating over `charAt(int)`.
> 
> In addition, this Pull Request proposes to replace the implementation of `Reader.of(CharSequence).read(char[] cbuf, int off, int len)` to invoke `CharSequence.getChars(next, next + n, cbuf, off)` instead of utilizing pattern matching for switch. Also, this PR proposes to implement `CharBuffer.getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)` as an alias for `CharBuffer.get(srcBegin, dst, dstBegin, srcEnd - srcBegin)`.
> 
> To ensure quality...
> * ...the method signature and JavaDocs are adapted from `AbstractStringBuilder.getChars(...)`.
> * ...this PR relies upon the existing tests for `Reader.of(CharSequence)`, as these provide sufficient coverage of all changes introduced by this PR.

Markus KARG has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 17 commits:

 - merge latest from master branch
 - Applied proposal by Daniel: If there's no change to this file the copyright year update could be reverted?
 - Applied workaround proposed by Joe: Using component @inheritDoc to enforce getChars section in JavaDocs
 - Applied changes proposed by Joe and Jaikiran: Using @inheritDoc to get JavaDocs without @since.
 - Applied changes proposed in response to Joe's CSR comments: 'understood for CharBuffer; I was thinking more of String, StringBuffer, and StringBuilder where there looks to be more textual similarities.'
 - Applied changes requestes by Alan: Aligning unit test for CharBuffer.getChars() with unit test for CharBuffer.chars()
 - Applied changes requested by Chen and Jaikiran: Unit tests for default implementation of CharSequence.getChars() and for CharBuffer.getChars()
 - Applied changes requested by Chen: 'We might need to specify the IOOBE behavior - when an IOOBE is thrown, some characters may be already transferred (this is important for concurrent char sequences)'
 - Applied changes requested by Alan: This sentence doesn't make sense, did something get deleted?
 - Applied changes requested by Alan: Copies chars from this sequence into the given destination array
 - ... and 7 more: https://git.openjdk.org/jdk/compare/b21b3a38...31537b7a

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Changes: https://git.openjdk.org/jdk/pull/21730/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21730&range=11
  Stats: 470 lines in 8 files changed: 399 ins; 59 del; 12 mod
  Patch: https://git.openjdk.org/jdk/pull/21730.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21730/head:pull/21730

PR: https://git.openjdk.org/jdk/pull/21730