Add packed_at() to PreProcessed Column Enum

[Gali-StarkWare]

This change is 

[Gali-StarkWare]

• Add packed_at() to PreProcessed Column Enum #360 👈 (View in Graphite)
• Move Preprocessed Columns Struct to Preprocessed File #359
• main

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[shaharsamocha7]

Reviewed 1 of 1 files at r1, all commit messages.
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[alon-f]

Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @Gali-StarkWare)

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stwo_cairo_prover/crates/prover/src/cairo_air/preprocessed.rs line 59 at r1 (raw file):

    pub fn packed_at(&self, vec_row: usize) -> PackedM31 {
        match self {
            PreProcessedColumn::IsFirst(column) => column.packed_at(vec_row),

blocked

[alon-f]

Reviewed 1 of 1 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @Gali-StarkWare)