cairo-lang-executable: borrow the target Sierra function instead of cloning

[0xLogicalx]

Stop cloning the first Sierra function when setting up the executable wrapper. Reuse the borrowed function reference when creating the wrapper info, keeping behaviour identical while avoiding redundant work.

[reviewable-StarkWare]

This change is 

[orizi]

@orizi reviewed 1 of 1 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @0xLogicalx)

[orizi]

Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @0xLogicalx)

---

crates/cairo-lang-executable/src/compile.rs line 231 at r1 (raw file):

    // Since we build the entry point asking for a single function - we know it will be first, and
    // that it will be available.
    let executable_func = &sierra_program.funcs[0];

run ./scripts/rust_fmt.sh

[0xLogicalx]

Ran ./scripts/rust_fmt.sh; formatting is applied and the updated changes are pushed. Thanks for the review!

[orizi]

not pushed apparently.

Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @0xLogicalx)