Analyzer non-nullability work - phase 1

[stereotype441]

This issue is a placeholder for non-nullability work we want to do in the analyzer that doesn't necessarily belong in phase 0 (#35586).

• Add definite assignment analysis for local variables Add definite assignment analysis for local variables #21811
• Analyzer's printing of function types will need to change to support nullability Analyzer's printing of function types will need to change to support nullability #35818
• Verify that no failures occur if IsEnabledByDefault.non_nullable is set to true.
• Logic to produce nullability fixes should be moved into analyzer_plugin Logic to produce nullability fixes should be moved into analyzer_plugin #35872

[srawlins]

I believe this can be closed.

[stereotype441]

Agreed