<i18n dev> RFR: 8364752: Class java.time.Instant cannot parse all ISO 8601 date formats

[Naoto Sato]

`Instant.parse()` is expected to use the offset zone pattern `+HH:mm:ss` (as defined by `DateTimeFormatterBuilder.appendOffsetId()`), but it fails to parse hour-only offsets such as `+02`. This is because the actual implementation uses `+HH:MM:ss` as the pattern. While replacing the pattern in the implementation as with the specification would allow hour-only offsets, it would also introduce compatibility issues, i.e., printing would omit the minutes field when it is zero. So, it is preferable to update the specification to match the implementation. A CSR has also been drafted for this change.

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Commit messages:
 - initial commit

Changes: https://git.openjdk.org/jdk/pull/26708/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26708&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8364752
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/26708.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26708/head:pull/26708

PR: https://git.openjdk.org/jdk/pull/26708