Port internal Postgres improvements to OSS

[rdeepak2002]

Pull Request type

• Bugfix
• Feature
• Refactoring (no functional changes, no api changes)
• Build related changes (Please run ./gradlew build --write-locks to refresh dependencies)
• Other (please describe):

NOTE: Please remember to run ./gradlew spotlessApply to fix any format violations.

Changes in this PR

Ports Postgres improvements and changes from internal bdp-maestro (PR #1500, commit 7324f560f) to align the OSS database layer with internal Postgres code paths.

Key changes:

• Replace GENERATED ALWAYS AS columns with explicit regular columns across all Flyway migrations
• Add explicit column binding in all INSERT/UPSERT statements (no longer relying on Postgres generated columns to extract fields from JSON blobs)
• Add SERIALIZABLE isolation level for race-condition-sensitive operations (FIRST_ONLY/LAST_ONLY run strategies, dequeue, workflow deletion)
• Use FNV-1a hash for timeline deduplication instead of hashCode() (more robust cross-JVM consistency)
• Add null-byte sanitization for Postgres TEXT/JSONB columns (PostgreSQL rejects \0 in text-based columns; timeline events are now sanitized via sanitizeString() before insertion)
• Match internal SQL formatting: tuple SET syntax, ON CONFLICT column qualification, and row_to_json() without redundant ::jsonb cast
• Rename maestro_output_data to output_data in order to match internal naming

Migration note

This is a breaking schema change. Flyway migrations are rewritten in-place (removing GENERATED columns), requiring a fresh database. Existing deployments must drop and recreate the database.

Test plan

• All existing tests pass
• Verified Postgres SQL query parity with internal bdp-maestro commit 7324f560f
• Manually verified explicit column binding matches internal Postgres paths
• Added null-byte sanitization tests ported from internal (testInsertStepInstanceSanitization, testUpdateStepInstanceSanitization)