Set device_id and settings_json from MDM

[lognaturel]

Exploration for #6581

This is intended to be a quick spike to explore how MDM works. To set settings_json, make sure to include both general and admin settings blocks.

Out of scope:

• Sending confirmation back to MDM, we can do this as a follow-on item

Todo:

• make sure all error handling is robust -- nothing should happen if invalid values are set

The easiest way I've found to try this is:

• Run Test DPC app
• Run adb shell dumpsys user to get profile info
• Update Android Studio run config to add --user N to Launch Flags where N is the user number for the managed user

In Test DPC, search for "managed configuration", then select Collect and identify all keys from manifest.

Why is this the best possible solution? Were any other approaches considered?

How does this change affect users? Describe intentional changes to behavior and behavior that could have accidentally been affected by code changes. In other words, what are the regression risks?

Do we need any specific form for testing your changes? If so, please attach one.

Does this change require updates to documentation? If so, please file an issue here and include the link below.

Before submitting this PR, please make sure you have:

• added or modified tests for any new or changed behavior
• run ./gradlew connectedAndroidTest (or ./gradlew testLab) and confirmed all checks still pass
• added a comment above any new strings describing it for translators
• added any new strings with date formatting to DateFormatsTest
• verified that any code or assets from external sources are properly credited in comments and/or in the about file.
• verified that any new UI elements use theme colors. UI Components Style guidelines

[lognaturel]

Doing something quick and dirty that keeps all of the functionality contained, I'm not suggesting we'd want to pass context into something like this