This patch implements a printer and parser for the S_WAITCNT mask. It
prints the mask in a human-readable format, showing the counter values
like `Vmcnt_<NUM>_Expcnt_<NUM>_Lgkmcnt_<NUM>`.
The format matches the printing style of S_WAITCNT_DEPCTR. For example:
```
S_WAITCNT .Vmcnt_0_Expcnt_0_Lgkmcnt_0
S_WAITCNT .Expcnt_0
S_WAITCNT .AllOff
```
Counters at their maximum value (meaning "don't wait") are omitted. When
all counters are at max, `.AllOff` is printed.
Co-Authored-By: Claude Opus 4 <noreply@anthropic.com>
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