[Utils][UpdateTestChecks] Generalize INLINEASM register class IDs with [[#]]
Modify update_mir_test_checks.py to automatically replace hardcoded register
class ID numbers in INLINEASM CHECK patterns with FileCheck's [[#]] numeric
substitution pattern. This ensures test stability even when the tabelgened
register class IDs change.
Before: INLINEASM &"...", 1234564 /* regdef:GPR_32 */, def %0
After: INLINEASM &"...", [[#]] /* regdef:GPR_32 */, def %0
Co-authored-by: Claude Sonnet 4.5