fix(bitmachine): fix frame data offsets send to tracker (fixes Execution reached a pruned branch)

[stringhandler]

Fixes some bugs where the data sent from the bitmachine to trackers would not start at the current cursor, resulting in some random junk being seen by the tracker. This doesn't have an effect on full programs, but when pruning this seems to generate an incorrect pruning, as seen in #337.

The following code now prunes and runs correctly:

fn add(elt: u32, acc: u32) -> u32 {
    let (_, sum): (bool, u32) = jet::add_32(elt, acc);
    sum
}

fn main() {
    let list: List<u32, 4> = list![5];
    let result: u32 = fold::<add, 4>(list, 0);
    assert!(jet::eq_32(result, 5));
}

Whereas previously it would fail on Execution failed: Execution reached a pruned branch: fd6503b9fd020b8d4ed75deb14cc05bbcb91da392ba4b675f2b2345dabb1cde5

Some excerpts from StderrTracker:

// Before fix
[  45] exec iden 2^32 → 2^32
       input 0x00000002
       output 0x00000005
       
// After fix
   [  45] exec iden 2^32 → 2^32
       input 0x00000005
       output 0x00000005

/// Before fix
[  46] exec iden (2^64? × 2^32?) × 1 → (2^64? × 2^32?) × 1
       input ((L(ε),R(0x00000005)),ε)
       output ((L(ε),L(ε)),ε)
       
// After fix
[  46] exec iden (2 × 2^32?) × 1 → (2 × 2^32?) × 1
       input ((0b0,R(0x00000005)),ε)
       output ((0b0,R(0x00000005)),ε)

I haven't tried it on @KyrylR 's specific SHRINCS test on that issue.

NOTE: I have based this off an older commit so I could test it with SimplicityHL, which doesn't compile with the latest rust-simplicity

NOTE: the unit test is written by Claude (Happy to remove it if needed)

[apoelstra]

In a4cbd56:

Let's just delete as_bit_iter. In the one place it's still called it's right after out_frame.reset_cursor() so it's equivalent to the new as_bit_iter_from_cursor.

[apoelstra]

In a4cbd56:

I think this new output_frame binding is unnecessary, but I like having it, because it borrows self.write for almost the entire interpreter function, guaranteeing that nothing in there modifies self.write.