Change the Destroy blanket impls to be more specific (#6098)

The main direction of this change is the edits to `destroy.carbon`
(matching in both prelude and min_prelude).

Previously there was a no-op blanket impl for `Destroy`, which hid all
missing implementations of `Destroy`. This does a few things:

- Sets up builtin aggregate destruction for struct and tuple types as
before, but also adds C++ class types and array types to the same
handling. (all as a TODO for actual implementation)
- Also maybe-unformed destruction, for now at least. (there's a chance I
may try a different approach on this, but the impl lookup wasn't working
as I'd hope in order to write it in code)
- Adds handlers for simple things that are easy to do in code: `type`,
`bool`, pointers. (because these are no-op destruction)
- Redirect `const T` destruction to `T` destruction.

This leaves as future issues:

- `partial T` destruction. (this can't be done similar to `const`
because it only works for non-`final` class types; I think `class`
definitions should just generate what's needed)
- Destruction of other prelude-provided types. (will probably come up as
we implement class destruction, that the adapted builtin type doesn't
implement `Destroy` -- but may end up special-casing that in a way that
moots it)

This moves the `&` operator from `facet_types.carbon` to
`convert.carbon` because more things need to handle type and now that
we're getting separate copy and destroy interfaces. It should be
low-cost (an interface and builtin) so hopefully this is the right
balance for complexity and re-use.

A few tests are also edited in order to focus them more on what they
intend to test, and avoid a `Destroy` dependency.

toolchain/check/testdata/function/generic/deduce_nested_facet_value.carbon

@@ -2,7 +2,7 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// INCLUDE-FILE: toolchain/testing/testdata/min_prelude/facet_types.carbon
+// INCLUDE-FILE: toolchain/testing/testdata/min_prelude/convert.carbon
 // TODO: Add ranges and switch to "--dump-sem-ir-ranges=only".
 // EXTRA-ARGS: --dump-sem-ir-ranges=if-present
 //
@@ -105,8 +105,8 @@ fn F() {
 // CHECK:STDOUT:     import Core//prelude/...
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %Core.Destroy: type = import_ref Core//prelude/parts/destroy, Destroy, loaded [concrete = constants.%Destroy.type]
-// CHECK:STDOUT:   %Core.BitAndWith: %BitAndWith.type.f2e = import_ref Core//prelude, BitAndWith, loaded [concrete = constants.%BitAndWith.generic]
-// CHECK:STDOUT:   %Core.import_ref.636: %type.as.BitAndWith.impl.Op.type = import_ref Core//prelude, loc14_42, loaded [concrete = constants.%type.as.BitAndWith.impl.Op]
+// CHECK:STDOUT:   %Core.BitAndWith: %BitAndWith.type.f2e = import_ref Core//prelude/parts/as, BitAndWith, loaded [concrete = constants.%BitAndWith.generic]
+// CHECK:STDOUT:   %Core.import_ref.636: %type.as.BitAndWith.impl.Op.type = import_ref Core//prelude/parts/as, loc25_42, loaded [concrete = constants.%type.as.BitAndWith.impl.Op]
 // CHECK:STDOUT:   %BitAndWith.impl_witness_table = impl_witness_table (%Core.import_ref.636), @type.as.BitAndWith.impl [concrete]
 // CHECK:STDOUT: }
 // CHECK:STDOUT: