PromQL service: fix time parse issue when using RFC3339 time format for querying.

[wankai123]

now, support the following format:

  "2026-01-20T03:27:18Z",
  "2026-01-20T03:27:18.0Z",
  "2026-01-20T03:27:18.000Z",
  "2026-01-20T03:27:18.123Z",
  "2026-01-20T11:27:18+08:00",
  "2026-01-20T11:27:18.0+08:00",
  "2026-01-20T11:27:18.123+08:00",
  "2026-01-20T11:27:18+0800",
  "2026-01-20T11:27:18.0+0800",
  "2026-01-20T11:27:18.123+0800",
  "2026-01-19T19:27:18-08:00",
  "2026-01-19T19:27:18.0-08:00",
  "2026-01-19T19:27:18.123-08:00",
  "2026-01-19T19:27:18-0800",
  "2026-01-19T19:27:18.0-0800",
  "2026-01-19T19:27:18.123-0800",
  "2026-01-20T03:27:18"

• If this pull request closes/resolves/fixes an existing issue, replace the issue number. Closes [Bug] RFC3339 w/ msec fails in PromQL #13675.
• Update the CHANGES log.

[Copilot]

Pull request overview

This PR fixes time parsing issues in the PromQL service when using RFC3339 time format for querying. The implementation replaces Joda Time's ISODateTimeFormat with Java's DateTimeFormatter to support various RFC3339 timestamp formats including different millisecond precision levels and timezone offset formats.

Changes:

• Created a custom RFC3339_FORMATTER using DateTimeFormatterBuilder to handle multiple RFC3339 timestamp variants
• Updated formatTimestamp2Millis method to use the new formatter with OffsetDateTime instead of Joda Time
• Added comprehensive test coverage for 17 different RFC3339 timestamp format variations

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
oap-server/server-query-plugin/promql-plugin/src/main/java/org/apache/skywalking/oap/query/promql/handler/PromQLApiHandler.java	Implements RFC3339_FORMATTER and updates timestamp parsing logic to use Java time APIs
oap-server/server-query-plugin/promql-plugin/src/test/java/org/apache/skywalking/promql/handler/PromQLApiHandlerTest.java	Adds test cases for various RFC3339 timestamp formats
docs/en/changes/changes.md	Documents the fix in the changelog

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.