refactor: upgrade project to remove warnings from Flutter 3.7

[Lyokone]

Description

With Flutter 3.7 avoid_as is deprecated and shouldn't be used anymore.
I've removed import_of_legacy_library_into_null_safe which is not recognized anymore
I've disabled synchronous gaps warnings for UI libraries but we should probably need to add them again and fixing this properly.

Updated all the examples to use the new material names.

Related Issues

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Breaking Change

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