boulder: Switch existing emul32 packages to `386` ISA

[ReillyBrogan]

This is a tracking issue for the fact that the rust boulder uses 386 for the ISA where the dlang boulder used x86. To resolve this (per discussion in Matrix), we need to do the following:

• Add duplicate provides to all emul32 packages to provide both 386 and x86 for all provides fields. Override the depends to use x86 INSTEAD OF 386 - boulder: Fix emul32 incompatibility with dlang boulder #223
• Rebuild all emul32 packages with that boulder
• Change the depends field to 386 instead of x86
• Rebuild all emul32 packages with that boulder
• Strip out the compat code so that emul32 package only provide and depend on 386
• (Optional) Rebuild emul32 packages again. This is optional because it will happen naturally over time.

[ermo]

We should take a look at whether we can utilise this approach to "wash out" the dlang boulder .stones when the time comes.

I am unclear on the consequences on the dlang side in terms of summit / libmoss.