Redundant Borrowing and Double Mapping in MappedCrossoverInsertMutator::mutate

[Aditya30ag]

Description

The MappedCrossoverInsertMutator::mutate function performs redundant operations when accessing and mapping the corpus input:

1. The testcase is borrowed twice using get_from_all(id)?.borrow_mut().
2. The input is loaded and mapped twice:
   • First to compute other_size
   • Second to retrieve the mapped input for mutation
3. Additional unnecessary unwrap() checks increase branching complexity.

This results in:

• Redundant function calls
• Extra borrow operations
• Unnecessary memory allocations
• Reduced readability

Expected Behavior

The mapped input and its size should be retrieved in a single borrow scope and used directly for mutation without re-loading or re-mapping.

[Aditya30ag]

@domenukk is this can be good to implement