Refactor - Replaces sub r11, imm with add r11, -imm

[Lichtso]

That way we only need one instruction which is specific to dynamic_stack_frames and R11.

In llvm the frame lowering will need to be adjusted to emit add r11, -imm instead of sub r11, imm:
https://github.com/solana-labs/llvm-project/blob/7b8db05b564faffb522434b73b7082662171f94a/llvm/lib/Target/SBF/SBFFrameLowering.cpp#L25

[codecov-commenter]

Codecov Report

Merging #488 (f4dcaac) into main (4c68373) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #488      +/-   ##
==========================================
+ Coverage   89.67%   89.69%   +0.01%     
==========================================
  Files          23       23              
  Lines       10105    10097       -8     
==========================================
- Hits         9062     9056       -6     
+ Misses       1043     1041       -2     

Impacted Files	Coverage Δ
src/interpreter.rs	98.20% <100.00%> (+0.28%)	⬆️
src/jit.rs	92.86% <100.00%> (+0.06%)	⬆️
src/verifier.rs	97.48% <100.00%> (-0.04%)	⬇️