[#12145] fix(test): prevent overlapping embedded server lifecycle on branch-1.3

[yuqi1129]

What changes were proposed in this pull request?

Backport #12146 to branch-1.3. Wait for the MiniGravitino server task to terminate before returning from stop(), and clean up resources even if shutdown fails. Add a regression test that delays server cleanup and verifies that stop() waits for it.

Why are the changes needed?

The HTTP port can close before the shared GravitinoEnv finishes shutting down. Starting the next embedded server during that window lets the previous shutdown close its catalog manager. This caused CatalogPaimonJdbcCredentialIT initialization to fail with CatalogManager is already closed on branch-1.3.

CI failure: https://github.com/apache/gravitino/actions/runs/34222422837/job/102048711221

Fix: #12145

Does this PR introduce any user-facing change?

No.

How was this patch tested?

• ./gradlew :integration-test-common:test --tests org.apache.gravitino.integration.test.TestMiniGravitino -PskipITs — 3 tests passed.
• ./gradlew spotlessApply :integration-test-common:check -PskipITs — 9 tests passed.
• git diff HEAD --check

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Code Coverage Report

Overall Project	69.27%	🟢
Files changed	No Java source files changed	-

Module	Coverage
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