fixes RawDialogRoute memory leak

[Dimilkalathiya]

part of #141198

• Fixes memory leak on RawDialogRoute
• Adds opt-in test

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[Dimilkalathiya]

Removing CurvedAnimation here since default animation is linear anyways

[polina-c]

Interesting. Can you explain it in more details? It is not obvious to me :)

[Dimilkalathiya]

Animation<double> we get from buildTransitions function is by default linear which is generated in abstract class TransitionRoute using AnimationController

So from my perspective it would be useless to add CurvedAnimation with linear curve since it is how Animation<double> will behave same by default, it would have been viable if it was anything except linear

does this make sense?

[polina-c]

@Piinks, can you review this or help to find someone who can confirm there is no hidden footgun there?

[chunhtai]

yes, Curve.linear is no-op

[Dimilkalathiya]

cc: @polina-c

[chunhtai]

LGTM

[chunhtai]

yes, Curve.linear is no-op