Fix MySQLRecordManager DataSource connection churn

[jianongHe]

Fixes #6567.

MySQLRecordManager was creating and destroying a TypeORM DataSource for every record-manager operation. Because DataSource owns the connection pool, that caused repeated pool creation during indexing and cleanup flows.

This PR changes MySQLRecordManager to:

• Lazily initialize and reuse one DataSource per record manager instance.
• Share the pending initialization promise across concurrent operations.
• Release QueryRunner instances after each operation.
• Add close() for explicit DataSource teardown.
• Close record managers after indexing and document-store vector deletion flows.

Verification:

• pnpm --dir packages/components exec jest --runInBand
  • 22 test suites passed, 875 tests passed
• pnpm --dir packages/server exec jest --runInBand
  • 31 test suites passed, 934 tests passed
• pnpm --filter flowise-components build
• pnpm --filter "./packages/server" build
• git diff --check
• prettier --check on changed files

Note:

• pnpm test at the monorepo root currently fails in packages/observe due to ExecutionTreeSidebar.test.tsx timing out in the full parallel run.
• The failing observe test is unrelated to this change and passes when run directly:
  pnpm --dir packages/observe exec jest src/features/executions/components/ExecutionTreeSidebar.test.tsx --runInBand --detectOpenHandles

[gemini-code-assist]

Code Review

This pull request refactors MySQLRecordManager to reuse a single DataSource instance across operations, shares pending initializations across concurrent operations, and ensures query runners are properly released. It also introduces a close method to clean up connections, which is integrated into the indexing and vector store deletion workflows. The review feedback highlights three key improvement opportunities: moving table name sanitization inside the try block in listKeys to prevent query runner leaks, clearing state variables synchronously in close() to avoid concurrent race conditions, and querying the database time directly within update() using the active query runner to prevent connection pool starvation.

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[itxaiohanglover]

Solid fix! The mock DataSource and QueryRunner tests are thorough — verifying initialize/destroy counts and connection lifecycle. This addresses the per-operation pool instantiation issue from #6567.