Update bundled JDK to 21.0.12+8

[reta]

Description

Update bundled JDK to 21.0.12+8 (tracking release binaries https://github.com/adoptium/temurin21-binaries/releases/tag/jdk-21.0.12%2B8)

Related Issues

Part of #22532

Check List

• Functionality includes testing.
• API changes companion pull request created, if applicable.
• Public documentation issue/PR created, if applicable.

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[github-actions]

PR Code Analyzer ❗

AI-powered 'Code-Diff-Analyzer' found issues on commit 82640b7.

Path	Line	Severity	Description
buildSrc/src/main/java/org/opensearch/gradle/test/DistroTestPlugin.java	80	high	Bundled JDK version changed from 21.0.11+10 to 21.0.12+8 (vendor: adoptium) for both SYSTEM_JDK_VERSION and GRADLE_JDK_VERSION. Per mandatory rule, all dependency version changes must be flagged. Maintainers should verify the new JDK artifact hash/signature matches the official Adoptium release for 21.0.12+8.
gradle/libs.versions.toml	6	high	bundled_jdk version changed from 21.0.11+10 to 21.0.12+8 (vendor: adoptium). Per mandatory rule, all dependency version changes must be flagged. This controls which JDK artifact is fetched at build time; maintainers should confirm the artifact origin and integrity (checksums/signatures) against the official Adoptium Temurin release.

The table above displays the top 10 most important findings.

Total: 2 | Critical: 0 | High: 2 | Medium: 0 | Low: 0

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Pull Requests Author(s): Please update your Pull Request according to the report above.

Repository Maintainer(s): You can bypass diff analyzer by adding label skip-diff-analyzer after reviewing the changes carefully, then re-run failed actions. To re-enable the analyzer, remove the label, then re-run all actions.

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⚠️ Note: The Code-Diff-Analyzer helps protect against potentially harmful code patterns. Please ensure you have thoroughly reviewed the changes beforehand.

Thanks.

[github-actions]

PR Reviewer Guide 🔍

Here are some key observations to aid the review process:

🧪 No relevant tests

🔒 No security concerns identified

✅ No TODO sections

🔀 No multiple PR themes

⚡ No major issues detected

[github-actions]

❌ Gradle check result for 7321be1: TIMEOUT

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[github-actions]

❌ Gradle check result for 7321be1: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[github-actions]

✅ Gradle check result for 7321be1: SUCCESS

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.03%. Comparing base (aff3489) to head (7321be1).
⚠️ Report is 21 commits behind head on 2.19.

Additional details and impacted files

@@             Coverage Diff              @@
##               2.19   #22572      +/-   ##
============================================
+ Coverage     71.92%   72.03%   +0.10%     
+ Complexity    66009    64520    -1489     
============================================
  Files          5342     5120     -222     
  Lines        307392   300237    -7155     
  Branches      44862    44102     -760     
============================================
- Hits         221105   216275    -4830     
+ Misses        67823    65865    -1958     
+ Partials      18464    18097     -367     

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[reta]

@cwperks @andrross would appreciate a look folks, when time permits, thanks!