[Backport 2.19] Guard eclipse() to spotless tasks and keep P2 mirror on pinned version (flow-framework)

[peterzhuamazon]

Backport f5ba22a from #1471.

[github-actions]

PR Code Analyzer ❗

AI-powered 'Code-Diff-Analyzer' found issues on commit 8b5b3ba.

⛔ Hard block: Issues at High severity or above will block this PR from merging.

Path	Line	Severity	Description
build.gradle	53	high	Dependency version change: 'com.diffplug.spotless:spotless-plugin-gradle' bumped from 7.0.2 to 8.10.1. Per mandatory supply chain policy, all dependency version changes must be flagged for maintainer verification regardless of apparent legitimacy.
formatter/formatting.gradle	44	high	New explicit dependency on Eclipse JDT version '4.34' introduced via eclipse('4.34'). Previously the version was resolved implicitly by the spotless plugin default. Pinning to a specific artifact version is a dependency change that must be verified per mandatory supply chain policy.

The table above displays the top 10 most important findings.

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

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