gh-145742: Manually emit _LOAD_FAST_BORROW to reduce stencil bloat

[corona10]

• Manually emit _LOAD_FAST_BORROW at JIT compile time, encoding the operand offset directly into the instruction instead of loading it from the GOT at runtime.
• This shrinks the generic case (oparg ≥ 8) from 28 bytes to 8 bytes and eliminates 27 stencil functions.
• I've compared machine code through godbolt: https://godbolt.org/z/3M9zKeosj

• Issue: Some (mostly) easy ways to reduce the size of JIT generated code #145742