[ML] Increase Test Coverage 7.12

[walterra]

Meta issue to summarize increased test coverage for 7.12

Jest unit tests

• Data Grid Mini Charts [ML] Column Charts Unit/Functional Tests #88176 (WR)

API integration tests

part of #63700

• Spaces API [ML] Initial API integration tests for ML jobs in spaces #84789 (RO)
• /api/ml/data_frame/analytics [ML] Data Frame Analytics: adds api integration tests for job creation #92101 [ML] Data Frame Analytic: adds api integration tests for _start and _stop endpoints #92532 (MA)
• /api/ml/ml_capabilities [ML] Adding ml_capabilities api tests #92786 (JG)

Functional tests

• Data Grid Mini Charts [ML] Column Charts Unit/Functional Tests #88176 (new canvasElement service) (WR)
• Scatterplot Matrix [ML] Data Frame Analytics: Adds scatterplot matrix to regression/classification results pages. #88353 (WR)
• Transforms: actions (start, delete) [ML] Add functional tests for Transform start/delete #92314 (QN)
• Transform: runtime mappings editor & runtime fields support [ML] Add functional tests for runtime mappings in Transforms #92738 (QN)

Accessibility tests

• ML [ML] Adds a11y tests for ML plugin #88323 (PH)

[elasticmachine]

Pinging @elastic/ml-ui (:ml)