[iOS][AIM] Add custom presentation and dismissal animation

This change replaces the default modal presentation of the AIM prototype
with a custom animation.

The new animation consists of:
- A fade-in for the main view.
- A slide-up animation for the input area upon presentation.
- The reverse for dismissal (fade-out and slide-down).

Key implementation details:
- Created `AIMPrototypePresentAnimator` and `AIMPrototypeDismissAnimator` to handle the custom transition logic.
- The `AIMPrototypeCoordinator` now acts as a `UIViewControllerTransitioningDelegate` to provide these custom animators.
- Introduced the `AIMPrototypeAnimationContextProvider` protocol to safely provide the necessary views from the `AIMPrototypeViewController` to the animators, decoupling the components.

Bug: None
Change-Id: Id8807471295a0f9f26e237a5dc9d9c2deaa6ce74
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6831462
Auto-Submit: Christian Xu <christianxu@chromium.org>
Commit-Queue: Christian Xu <christianxu@chromium.org>
Reviewed-by: Radu Nitescu <radunitescu@google.com>
Cr-Commit-Position: refs/heads/main@{#1499580}