RFR: 8306623: (bf) CharBuffer::allocate throws unexpected exception type with some CharSequences

[Brian Burkhalter]

When appending a `CharBuffer`, perform a specific check for buffer overflow before invoking `put()`.

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Commit messages:
 - 8306623: (bf) CharBuffer::allocate throws unexpected exception type with some CharSequences

Changes: https://git.openjdk.org/jdk/pull/13632/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13632&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8306623
  Stats: 65 lines in 2 files changed: 39 ins; 0 del; 26 mod
  Patch: https://git.openjdk.org/jdk/pull/13632.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13632/head:pull/13632

PR: https://git.openjdk.org/jdk/pull/13632