Fix #54047

For legacy reasons (presumably), Windows does not permit files name aux.

Instead of finding aux-build files in `auxiliary`, we now search for an
`aux` directory relative to the test. So if your test is
`compile-fail/foo.rs`, we would look in `compile-fail/aux`.  Similarly,
we ignore the `aux` directory when searching for tets.

While adding PowerPC64 support it was noticed that some testcases should
just use target_pointer_width, and others should select between
x86 and !x86.

This adds support for big endian and little endian PowerPC64.
make check runs clean apart from one big endian backtrace issue.

Now that support has been removed, all lingering use cases are renamed.

Adds AArch64 knowledge to:
* configure,
* make files,
* sources,
* tests, and
* documentation.

All deprecation warnings have been converted to errors. This includes
the warning for multiple cfgs on one item. We'll leave that as an error
for some period of time to ensure that all uses are updated before the
behavior changes from "or" to "and".

This commit moves reflection (as well as the {:?} format modifier) to a new
libdebug crate, all of which is marked experimental.

This is a breaking change because it now requires the debug crate to be
explicitly linked if the :? format qualifier is used. This means that any code
using this feature will have to add `extern crate debug;` to the top of the
crate. Any code relying on reflection will also need to do this.

Closes #12019

[breaking-change]

Closes #4545
Closes #5791
Closes #6470
Closes #8044

The tests have consts defined both before and after their uses in order
to prevent bugs that depend on the order in which they are translated.