Improve HLIL for signed non-negative compare

Discussed in https://github.com/Vector35/binaryninja-api/discussions/2892

^{Originally posted by gixslayer January 28, 2022}
Tested on version 3.0.3233. I have a simple piece of x86_64 code that essentially performs the following:

int32_t value;
// code that assigns to and uses value
return value >= 0;

This greater or equal to zero check is implemented as:

; load value into eax
not eax
shr eax, 0x1f
; return

So effectively it just isolates the sign bit and checks that.
This is correctly shown in the disassembly and BNIL, but the HLIL also shows this in a very verbose manner:

rax_25 = (not.d(value) u>> 0x1f).b

It would be nice if the HLIL would display it as something similar to value s>= 0. Not sure if this is just an edge case, but it feels common enough to warrant some QoL readability improvements for HLIL.

The issue names HLIL and BNIL but no source files or tests; begin by locating the HLIL logic that represents signed non-negative comparisons and the related regression tests. The work is done when the shown sign-bit sequence is rendered as an equivalent signed non-negative comparison without degrading the existing disassembly or BNIL output.