[test] Fix flaky FlussAdminITCase.testDynamicConfigs

[Kaixuan-Duan]

Purpose

Linked issue: close #3127

Brief change log

• Modify FlussAdminITCase.testDynamicConfigs test method
• Add a verify step that first checks cluster config has been updated before checking table info
• Use describeClusterConfigs to confirm cluster config is updated first, then verify table info reflects latest config
• Avoid the race condition where LakeCatalogDynamicLoader hasn't finished reconfiguring when table info is queried

Tests

• FlussAdminITCase#testDynamicConfigs test passed and runs stably
• Run multiple times to verify test stability

./mvnw -pl fluss-client -Dtest='FlussAdminITCase#testDynamicConfigs' -DfailIfNoTests=false test

API and Format

Documentation