Add builtin functions for destroy, with special requirements in facet types (#6035)

This is in support of a goal of changing the blanket `destroy` impl to
use (roughly):

```
private fn CanAggregateDestroy() -> type = "type.can_aggregate_destroy";

// Handles aggregate type destruction.
impl forall [AggregateDestroyT:! CanAggregateDestroy()] AggregateDestroyT as Destroy {
  fn Op[addr self: Self*]() = "type.aggregate_destroy";
}
```

That isn't done here because there's still other issues that migrating
raises. What this *does* do is add the builtin functions, and in
particular, support to `FacetTypeInfo` to make `CanAggregateDestroy`
work.

The "special requirement" approach in `FacetTypeInfo` allows us to
support restricting a blanket impl under the current approach of impls.
Maybe we'll find a cleaner approach that can work in the future, but
this fits into the current model by propagating similar to other
requirements. I'm using an enum mask because we have a number of similar
things to add (e.g. copy, move) but I'm not sure we need a full vector.

A few alternatives considered were:

- Supporting syntax more like `where .Self impls
TypeCanAggregateDestroy(.Self, SupportedInterface,
UnsupportedInterface)`. I think it'd be a little cleaner, but requires
better compile-time evaluation in order to assess the type of the call.
Right now it's expected to be a `FacetType` too early to make this work,
and I was concerned about pouring too much more time down this route.
- Providing an actual interface, in particular doing name lookup back
into `Core.` for an interface. This would've added name lookup overhead,
and the question of whether an `impl` exists.
- Generating an interface. This avoids the name lookup, but would still
raise the question of whether an `impl` should also be generated. Work
I've previously done generating interfaces for class destruction also
feels complex to both write and understand (an unfortunate issue).
- Still modeling as an `ImplsConstraint`, for example by defining a
special `InterfaceId::CanAggregateDestroy = -2` similar to what we do on
other ids. I was hesitant because of how this expands the number of
modes of `InterfaceId`, and things for consuming code to watch out for,
for what feels like a relatively niche set of use-cases that are only
interface-like.

---------

Co-authored-by: Dana Jansens <danakj@orodu.net>

toolchain/sem_ir/builtin_function_kind.cpp

@@ -154,6 +154,14 @@ struct AnyFloat {
   }
 };
 
+// Constraint that allows an arbitrary type.
+struct AnyType {
+  static auto Check(const File& /*sem_ir*/, ValidateState& /*state*/,
+                    TypeId /*type_id*/) -> bool {
+    return true;
+  }
+};
+
 // Constraint that requires the type to be the type type.
 using Type = BuiltinType<TypeType::TypeInstId>;
 
@@ -601,6 +609,19 @@ constexpr BuiltinInfo BoolNeq = {"bool.neq",
 constexpr BuiltinInfo TypeAnd = {"type.and",
                                  ValidateSignature<auto(Type, Type)->Type>};
 
+// Destroys a primitive type. The argument must be destructible, which can be
+// checked with `type.can_aggregate_destroy`.
+// TODO: The argument should be `addr self: Self*`. Consider modifying
+// `ValidateSignature` to more fully enforce the structure.
+constexpr BuiltinInfo TypeAggregateDestroy = {
+    "type.aggregate_destroy",
+    ValidateSignature<auto(PointerTo<AnyType>)->NoReturn>};
+
+// Returns a facet type that's used to determine whether a type can use
+// `type.aggregate_destroy`.
+constexpr BuiltinInfo TypeCanAggregateDestroy = {
+    "type.can_aggregate_destroy", ValidateSignature<auto()->Type>};
+
 }  // namespace BuiltinFunctionInfo
 
 CARBON_DEFINE_ENUM_CLASS_NAMES(BuiltinFunctionKind) {
@@ -713,6 +734,10 @@ auto BuiltinFunctionKind::IsCompTimeOnly(const File& sem_ir,
     case TypeAnd:
       return true;
 
+    case TypeCanAggregateDestroy:
+      // Type queries must be compile-time.
+      return true;
+
     default:
       // TODO: Should the sized MakeType functions be compile-time only? We
       // can't produce diagnostics for bad sizes at runtime.