Add duo_auto_mode_enabled cascading setting database migrations

What does this MR do and why?

This MR adds a new duo_auto_mode_enabled column to support a cascading setting that allows instances/groups/projects to enable/disable auto mode in the CLI/IDE surfaces. This MR specifically handles the migrations associated with the new column.

The implementation and logic for this changes will be introduced in a follow up MR (adding link sooon) and the UI changes to display the settings will be added in a third MR. The initial direction of this MR was introduced/reviewed (skimmed) here: Add duo_auto_mode UI toggle to Duo settings (!253317 - merged), but splitting it into smaller pieces will make reviews much easier.

References

Partially closes: Auto mode: duo_auto_mode cascading setting, cap... (#618088 - closed)

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