[llvm] [TableGen] Add `PreferSmallerInstructions` for Targets. (PR #83587)

[Alfie Richards via llvm-commits]

AlfieRichardsArm wrote:

```CPP
-        if (A.couldMatchAmbiguouslyWith(B, Target)) {
+        bool PreferSmallerInstructions =
+            AsmParser->getValueAsBit("PreferSmallerInstructions");
+        if (A.couldMatchAmbiguouslyWith(B, PreferSmallerInstructions)) {
```

> @s-barannikov: Same for shouldBeMatchedBefore above.

Fixed.

https://github.com/llvm/llvm-project/pull/83587