[ML] Propagate execution context from ML

[lizozom]

Solutions can now utilize useExecutionContext to make sure all outgoing requests (search, saved objects) are properly traced back to a page and an entity (in ES, APM and Fullstory).

// Application ID and current URL are traced automatically.
useExecutionContext({
   type: 'application',
   page: 'editor'
   id: savedVis.id ?? 'new',
});

• Call useExecutionContext on the top most react component that renders each page (list, editor, etc).
  • The page names should be short and consistent (no unique identifiers).
  • The id field can be used to track the main entity handled by the page (for example the displayed dashboard). Leave it empty if not applicable (For example on a listing page).
• If the application code is being rendered within an embeddable or nested elsewhere, make sure to attach child context properly
• See the testing instructions to make sure data is sent properly to APM.

[elasticmachine]

Pinging @elastic/ml-ui (:ml)