`crucible-mir`: Remove `clone` shim logic for arrays

[RyanGlScott]

As of rust-lang/rust#86041, Clone impls for array types are now implemented in library code rather than using clone shims. As such, the TyArray case in crucible-mir's clone shim logic is now unreachable, and we can remove it to simplify things:

crucible/crucible-mir/src/Mir/TransCustom.hs

Lines 2138 to 2155 in c76f025

	cloneShimDef (TyArray ty len) parts
	| [part] <- parts = CustomMirOp $ \ops -> do
	lv <- case ops of
	[Move lv] -> return lv
	[Copy lv] -> return lv
	[op] -> mirFail $ "cloneShimDef: expected lvalue operand, but got " ++ show op
	_ -> mirFail $ "cloneShimDef: expected exactly one argument, but got " ++ show (length ops)
	-- The argument to the clone shim is `&[T; n]`. The clone method for
	-- elements requires `&T`, computed as `&arg[i]`.
	let elementRefRvs = map (\i ->
	Ref Shared (LProj (LProj lv Deref) (ConstantIndex i len False)) "_") [0 .. len - 1]
	elementRefExps <- mapM evalRval elementRefRvs
	elementRefOps <- mapM (\expr -> makeTempOperand (TyRef ty Immut) expr) elementRefExps
	clonedExps <- mapM (\op -> callExp part [op]) elementRefOps
	Some tpr <- tyToReprM ty
	buildArrayLit tpr clonedExps
	| otherwise = CustomOp $ \_ _ -> mirFail $
	"expected exactly one clone function for in array clone shim, but got " ++ show parts

See GaloisInc/mir-json#197 for the corresponding mir-json-side issue.