As before, add `MetaSized` and `PointeeSized` traits to all of the
non-minicore `no_core` tests so that they don't fail for lack of
language items.

As core uses an extern type (`ptr::VTable`), the default `?Sized` to
`MetaSized` migration isn't sufficient, and some code that previously
accepted `VTable` needs relaxed to continue to accept extern types.

Similarly, the compiler uses many extern types in `rustc_codegen_llvm`
and in the `rustc_middle::ty::List` implementation (`OpaqueListContents`)
some bounds must be relaxed to continue to accept these types.

Unfortunately, due to the current inability to relax `Deref::Target`,
some of the bounds in the standard library are forced to be stricter than
they ideally would be.

Adding a sizedness supertrait shouldn't require multiple vtables so
shouldn't be linted against.

Opting-out of `Sized` with `?Sized` is now equivalent to adding a
`MetaSized` bound, and adding a `MetaSized` or `PointeeSized` bound
is equivalent to removing the default `Sized` bound - this commit
implements this change in `rustc_hir_analysis::hir_ty_lowering`.

`MetaSized` is also added as a supertrait of all traits, as this is
necessary to preserve backwards compatibility.

Unfortunately, non-global where clauses being preferred over item bounds
(where `PointeeSized` bounds would be proven) - which can result in
errors when a `PointeeSized` supertrait/bound/predicate is added to some
items. Rather than `PointeeSized` being a bound on everything, it can
be the absence of a bound on everything, as `?Sized` was.

With `MetaSized` bounds replacing `?Sized` and being added as a
supertrait, the same relaxations applied to the standard library must be
applied to minicore.

`Sized` errors are currently stashed to improve diagnostics and this
must happen with `{Meta,Pointee}Sized` too to maintain diagnostic
output.

Given the necessary additions of bounds to these traits and their impls
in the standard library, it is necessary to add `MetaSized` bounds to
the obligation which is proven as part of checking for dyn
dispatchability.

Like `Sized` diagnostics, sorting `MetaSized` and `PointeeSized`
diagnostics last prevents earlier more useful diagnostics from being
skipped because there has already been error tainting.

When printing impl headers in a diagnostic, the compiler has to account
for `?Sized` implying `MetaSized` and new `MetaSized` and `PointeeSized`
bounds.

When `sized_hierarchy` is enabled, rustc should print `MetaSized` or
`PointeeSized` instead of `?Sized` in opaques.

These tests necessarily need to change now that `?Sized` is not
sufficient to accept extern types and `PointeeSized` is now necessary. In
addition, the `size_of_val`/`align_of_val` test can now be changed to
expect an error.

These tests expected entirely unconstrained parameters and their `?Sized`
bounds are no longer sufficient to achieve that.

It seems like generics from `non_lifetime_binders` don't have any default
bounds like normal generics, so all of the `?Sized` relaxations need
to be further relaxed with `PointeeSized` for this test to be the
equivalent of before.

This test no longer crashes the compiler as `Box` no longer accepts
`PointeeSized`-types. It eventually could, but not because of
`Deref::Target` currently, so this doesn't fail anymore and there wasn't
an obvious to add new types to make it continue to fail because `Deref`
is special.

These tests just need blessing, they don't have any interesting behaviour
changes.

Some of these tests have new errors because `LegacyReceiver` cannot be
proven to be implemented now that it is also testing for `MetaSized` -
but this is just a consequence of the other errors in the test.

Extend the fast path for `Sized` traits to include constness and
`MetaSized`.

As a performance optimization, skip elaborating the supertraits of
`Sized`, and if a `MetaSized` obligation is being checked, then look for
a `Sized` predicate in the parameter environment. This makes the
`ParamEnv` smaller which should improve compiler performance as it avoids
all the iteration over the larger `ParamEnv`.

`nominal_obligations` calls `predicates_of` on a `Sized` obligation,
effectively elaborating the trait and making the well-formedness checking
machinery do a bunch of extra work checking a `MetaSized` obligation is
well-formed, but given that both `Sized` and `MetaSized` are built-ins,
if `Sized` is otherwise well-formed, so `MetaSized` will be.

These should never be shown to users at the moment.

Some rustdoc tests are `no_core` and need to have `MetaSized` and
`PointeeSized` added to them.

As before, updating types using extern types to use `PointeeSized`
bounds.

Unexpected Clippy lint triggering is fixed in upcoming commits but
is necessary for `cfg(bootstrap)`.

Existing lints that had special-casing for `Sized` predicates ought
to have these same special cases applied to `MetaSized` predicates.

One clippy test is `no_core` and needs to have `MetaSized` and
`PointeeSized` added to it.

As in many previous commits, adding the new traits to minicore, but this
time for cranelift and gcc.

It's unclear why this change in miri is necessary.

These error messages include lines of the standard library which have
changed and so need updated.