feat: Implement Table row update

[ApostolisFalaras]

Description

Update a stored row while keeping all affected indexes consistent.

Tasks

• Locate the existing row
• Validate replacement values
• Determine which indexed keys change
• Remove obsolete index entries
• Write the updated row
• Insert replacement index entries
• Update schema statistics
• Roll back changes on failure

Acceptance Criteria

• Updated values are persisted.
• Changed index keys are reflected in every index.
• Unchanged indexes are not modified unnecessarily.
• Failed updates do not leave inconsistent index state.

Depends On

• feat: Implement Table row insertion
• feat: Implement Index entry deletion