This patch implements the handling of inline builtin functions in CIR.
There is a known limitation in CIR where direct calls to shadowed inline
builtin functions are generated instead of the intrinsic. This is
expected to be fixed by the introduction of the nobuiltin attribute in a
future patch.

Added support for ConditionalOperator, BinaryConditionalOperator and
OpaqueValueExpr as lvalue.

Implemented support for ternary operators with one branch being a throw
expression. This required weakening the requirement that the true and
false regions of the ternary operator must terminate with a `YieldOp`.
Instead the true and false regions are now allowed to terminate with an
`UnreachableOp` and no `YieldOp` gets emitted when the block throws.

This adds the code needed to emit alloca operations for variable length
array local variables and the necessary calls to stacksave and
stackrestore to adjust the local stack as the array variables go in an
out of scope.

This adds support for calling virtual destructors.

This adds the necessary cleanup handling to get class destructors to
call the destructor for fields that require it.

This PR adds new `FuncOp` attributes (`coroutine` and `builtin`) and
begins the implementation of the `emitCoroutineBody` function. Feature
markers were also added for guidance in future PRs.

This adds support for emitting pseudo-macro expressions that represent
some form of the name of a function (such as `__func__` or
`__PRETTY_FUNCTION__`) as l-values.

Implement the GenericSelectionExpr for AggregateExpr

This adds support for handling global variables with non-trivial
constructors. The constructor call is emitted in CIR as a 'ctor' region
associated with the global definition. This form of global definition
cannot be lowered to LLVM IR yet.

A later change will add support in LoweringPrepare to move the ctor code
into a __cxx_global_var_init() function and add that function to the
list of global global ctors, but for now we must stop at the initial CIR
generation.

Implement the ChooseExpr for aggregate expr