InstCountCI: Support multiple instructions in the tests

There are some cases where we want to test multiple instructions where
we can do optimizations that would overwise be hard to see.

eg:
```asm
; Can be optimized to a single stp
push eax
push ebx

; Can remove half of the copy since we know the direction
cld
rep movsb

; Can remove a redundant insert
addss xmm0, xmm1
addss xmm0, xmm2
```

This lets us have arbitrary sized code in instruction count CI, with the
original json key becoming only a label if the instruction array is
provided.

There are still some major limitations to this, instructions that
generate side-effects might have "garbage" after the end of the block
that isn't correctly accounted for. So care must be taken.

Example in the json
```json
"push ax, bx": {
  "ExpectedInstructionCount": 4,
  "Optimal": "No",
  "Comment": "0x50",
  "x86Insts": [
    "push ax",
    "push bx"
  ],
  "ExpectedArm64ASM": [
    "uxth w20, w4",
    "strh w20, [x8, #-2]!",
    "uxth w20, w7",
    "strh w20, [x8, #-2]!"
  ]
}
```

FEXCore/Source/Interface/Core/Frontend.cpp

@@ -1095,7 +1095,7 @@ const uint8_t *Decoder::AdjustAddrForSpecialRegion(uint8_t const* _InstStream, u
   return _InstStream - EntryPoint + RIP;
 }
 
-void Decoder::DecodeInstructionsAtEntry(uint8_t const* _InstStream, uint64_t PC, std::function<void(uint64_t BlockEntry, uint64_t Start, uint64_t Length)> AddContainedCodePage) {
+void Decoder::DecodeInstructionsAtEntry(uint8_t const* _InstStream, uint64_t PC, uint64_t MaxInst, std::function<void(uint64_t BlockEntry, uint64_t Start, uint64_t Length)> AddContainedCodePage) {
   FEXCORE_PROFILE_SCOPED("DecodeInstructions");
   BlockInfo.TotalInstructionCount = 0;
   BlockInfo.Blocks.clear();
@@ -1133,6 +1133,10 @@ void Decoder::DecodeInstructionsAtEntry(uint8_t const* _InstStream, uint64_t PC,
 
   AddContainedCodePage(PC, CurrentCodePage, FHU::FEX_PAGE_SIZE);
 
+  if (MaxInst == 0) {
+    MaxInst = CTX->Config.MaxInstPerBlock;
+  }
+
   while (!BlocksToDecode.empty()) {
     auto BlockDecodeIt = BlocksToDecode.begin();
     uint64_t RIPToDecode = *BlockDecodeIt;
@@ -1195,9 +1199,9 @@ void Decoder::DecodeInstructionsAtEntry(uint8_t const* _InstStream, uint64_t PC,
         CanContinue = true;
       }
 
-      bool FinalInstruction = DecodedSize >= CTX->Config.MaxInstPerBlock ||
+      bool FinalInstruction = DecodedSize >= MaxInst ||
           DecodedSize >= DefaultDecodedBufferSize ||
-          TotalInstructions >= CTX->Config.MaxInstPerBlock;
+          TotalInstructions >= MaxInst;
 
       if (DecodeInst->TableInfo->Flags & FEXCore::X86Tables::InstFlags::FLAGS_SETS_RIP) {
         // If we have multiblock enabled