RFR: 8326627: Document Double/Float.valueOf(String) behaviour for numeric strings with non-ASCII digits

[Naoto Sato]

Clarifying the behavior for non-ASCII digits in Double/Float.valueOf(String) method descriptions. A draft CSR has also been created.

-------------

Commit messages:
 - initial commit

Changes: https://git.openjdk.org/jdk/pull/18526/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18526&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8326627
  Stats: 33 lines in 4 files changed: 22 ins; 8 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/18526.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18526/head:pull/18526

PR: https://git.openjdk.org/jdk/pull/18526