* Use `curly_braces_in_flow_control_structures` for `material`

* include test/material

* add back removed comments

This reverts commit d056500b.

This reverts commit 31de052e.

This reverts commit e2490f29.

Update samples to use repo analysis options, Fix sample templates and a ton of analyzer issues (#77868)

Adds MediaQuery.maybeOf to replace calling MediaQuery.of(context, nullOk: true), and removes the nullOk parameter. Also changes MediaQuery.of to return a non-nullable value, and removes many instances of the ! operator, reducing the possible places where a null dereference could occur.

* migrate material to nullsafety

* address review comments

* address review comments

* fix build