Add tools/split_gaps.py

[vagnertxr]

Reports the .text ranges that splits.txt does not claim yet, and which data each one references.

Carving a translation unit out of an auto_* blob is the first step of every new decomp, and the hard part is proving where the unit ends. Data that no other block touches settles it: a hole whose constants belong to nobody else is a translation unit.

Two things it gets right that a naive version does not:

• Exclusivity is decided per symbol, not per hole. A single hole in .sdata2 routinely holds constants for several units, so testing the hole as a whole reports everything as shared and hides every boundary in it.
• Assembly left behind by dtk when a unit disappears from splits.txt is skipped, since a stale .s looks like a second user of every constant it mentions.

On RSBE01_02 today it finds 44 unclaimed ranges, 42 of which own data outright. The smallest is 0x8002F188-0x8002F5B8 between gf_task_scheduler and gf_thread: 1072 bytes, 2 functions, owning .sdata2 at 0x805A1570, whose contents are the BT.601 coefficients (1.164 / 1.596 / 0.391 / 0.813 / 2.018) — a YUY2 to RGBA8 tile converter.

python tools/split_gaps.py
python tools/split_gaps.py --min-size 1024 --exclusive-only

Needs a build first, so build/<version>/asm exists and matches splits.txt.