Currently a small SQL change in a model automatically triggers a full refresh. This PR supports specifying a "change mode" on models, which governs behavior when the model logic changes.

Resolves: https://github.com/rilldata/rill-private-issues/issues/1635

It supports these options:
reset: changing the model automatically leads to a full refresh (default, current behavior)
manual: changing the model stops refreshes until a manual incremental or full refresh is run
patch: changing the model automatically changes to the new logic without a reset

type: model
change_mode: {reset|manual|patch}

Checklist:

• Covered by tests
• Ran it and it works as intended
• Reviewed the diff before requesting a review
• Checked for unhandled edge cases
• Linked the issues it closes
• Checked if the docs need to be updated
• Intend to cherry-pick into the release branch
• I'm proud of this work!