Common structure for concrete and extern enum lowering

[eytan-starkware]

This is in preparation for having a common trait for common code

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Stack:

• Enum matching lowering of variant blocks in a common trait #7739
• Common structure for concrete and extern enum lowering #7738 ⬅

⚠️ Part of a stack created by spr. Do not merge manually using the UI - doing so may have unexpected results.

[reviewable-StarkWare]

This change is 

[orizi]

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

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crates/cairo-lang-lowering/src/lower/lower_match.rs line 1341 at r1 (raw file):

/// A context for lowering patterns of enum variants in a match statement.
struct EnumVariantBuilderContext<'a> {

add fn new for this struct.
most construction now id duplicated as well.

Code quote:

struct EnumVariantBuilderContext<'a> {

[orizi]

Reviewed all commit messages.
Reviewable status: 0 of 1 files reviewed, 2 unresolved discussions (waiting on @eytan-starkware and @TomerStarkware)

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crates/cairo-lang-lowering/src/lower/lower_match.rs line 1207 at r2 (raw file):

        get_underscore_pattern_path_and_mark_unreachable(ctx, match_arms, match_type);
    let variant_map =
        get_variant_to_arm_map(ctx, match_arms, extern_enum.concrete_enum_id, match_type)?;

move into the new fn.

Code quote:

    let otherwise_variant =
        get_underscore_pattern_path_and_mark_unreachable(ctx, match_arms, match_type);
    let variant_map =
        get_variant_to_arm_map(ctx, match_arms, extern_enum.concrete_enum_id, match_type)?;

[orizi]

Reviewed 1 of 1 files at r3, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @TomerStarkware)