8383175: (tz) Update Timezone Data to 2026b

[gnu-andrew]

This is a clean backport of the two part tzdata2026b update. The comment changes were applied in one commit and the actual change in a follow-up, which are combined in this one PR to simplify backports to the update releases. I see similar being done in openjdk/jdk26u#186

This is not yet ready for integration due to test failures:

$ make run-test TEST="jtreg:java/text/Format java/util/TimeZone sun/util/calendar sun/util/resources"
...
==============================
Test summary
==============================
   TEST                                              TOTAL  PASS  FAIL ERROR  SKIP   
   jtreg:test/jdk/java/text/Format                     133   133     0     0     0   
   jtreg:test/jdk/java/util/TimeZone                    27    25     0     0     2   
   jtreg:test/jdk/sun/util/calendar                      3     3     0     0     0   
   jtreg:test/jdk/sun/util/resources                    22    22     0     0     0   
==============================
TEST SUCCESS

I believe backporting JDK-8382020 should fix at least some of this, but doing so breaks the build at present due to JDK-8384043 which does not yet have a final fix (it was fixed and then backed out so far): JDK-8384043 was resolved and applying this change on top of these two fixes in #548 gives the clean test run above.

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Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• JDK-8383473 needs maintainer approval
• JDK-8383175 needs maintainer approval

Integration blocker

 ⚠️ Dependency #548 must be integrated first

Issues

• JDK-8383175: (tz) Update Timezone Data to 2026b (Enhancement - P3)
• JDK-8383473: Follow on from tzdata2026b time change to include temporary hack BC time change (Bug - P4)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk25u-dev.git pull/547/head:pull/547
$ git checkout pull/547

Update a local copy of the PR:
$ git checkout pull/547
$ git pull https://git.openjdk.org/jdk25u-dev.git pull/547/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 547

View PR using the GUI difftool:
$ git pr show -t 547

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk25u-dev/pull/547.diff

[bridgekeeper]

👋 Welcome back andrew! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[openjdk]

This backport pull request has now been updated with issue from the original commit.

[gnu-andrew]

/issue add 8383473

[openjdk]

@gnu-andrew
Adding additional issue to issue list: 8383473: Follow on from tzdata2026b time change to include temporary hack BC time change.