[X86] Fix wrong ImmT in several instructions and add assertion (#185461)
Follow-up to #185254:
Several instructions inherited ImmT=Imm8 from *Ii8Base/*Ii8 classes
without having an actual immediate operand. This made
X86MCCodeEmitter::emitMemModRMByte compute ImmSize=1 instead of 0:
```
int ImmSize = !Disp.isImm() && X86II::hasImm(TSFlags)
? X86II::getSizeOfImm(TSFlags)
: 0;
```
biasing RIP-relative displacements by one byte (e.g. foo-0x5 instead
of foo-0x4).
Affected instructions:
- VCVTHF82PH (via AVX512XDIi8Base): has memory forms, wrong relocations
- V[U]COMIS{S,D,H}Zrrb (via AVX512P{S,D}Ii8Base): reg-only, latent
- MMX_MOV{DQ2Q,Q2DQ}rr and variants (via MMXSDIi8/MMXS2SIi8): reg-only,
latent
Fix by replacing the *Ii8Base/*Ii8 classes with their prefix-only
equivalents (TB, XD, XS, PD) and setting ExeDomain explicitly where
needed.
Add an assertion in encodeInstruction to catch future TSFlags/operand
ImmType mismatches: after consuming all operands in the Form-specific
switch, if `hasImm(TSFlags)` is true but `RemainingOps` is 0 and the
Form
isn't one that handles immediates internally (RawFrm, AddCCFrm,
RawFrmImm8, RawFrmImm16, RawFrmMemOffs), the assertion fires. For
example, `VCOMISDZrrb` has `Form=MRMSrcReg` and `ImmT=Imm8` (from
AVX512PDIi8Base), but after consuming both XMM operands CurOp equals
NumOps, leaving RemainingOps=0 with no immediate to emit.
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