feat(corelib): FnSnapshotImpl

[julio4]

This implementation allows to use snapshot of type that implements Fn.
It is useful when we want to pass an @Fn to a function that expects an FnOnce for example.

[reviewable-StarkWare]

This change is 

[orizi]

Reviewable status: 0 of 1 files reviewed, 1 unresolved discussion (waiting on @julio4)

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corelib/src/ops/function.cairo line 40 at r1 (raw file):

/// Implementation of `Fn` for snapshots.
/// This allows using a snapshot of a type that implements `Fn` as a function.
impl FnSnapshotImpl<T, Args, impl F: Fn<T, Args>> of Fn<@T, Args> {

add a minimal test that now works and previously did not at:
corelib/src/test/language_features/closure_test.cairo

[orizi]

Reviewable status: 0 of 1 files reviewed, 2 unresolved discussions (waiting on @julio4)

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a discussion (no related file):
@TomerStarkware for 2nd eye.

[julio4]

Reviewable status: 0 of 2 files reviewed, 2 unresolved discussions (waiting on @orizi)

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corelib/src/ops/function.cairo line 40 at r1 (raw file):

Previously, orizi wrote…

add a minimal test that now works and previously did not at:
corelib/src/test/language_features/closure_test.cairo

Done.

[orizi]

Reviewed 1 of 1 files at r1, 1 of 1 files at r2, all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @julio4)

[TomerStarkware]

Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @julio4)

[orizi]

Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @julio4)