This commit removes pretty-expanded from all tests that wind up calling panic!
one way or another now that its internals are unstable.

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

Now that features must be declared expanded source often does not compile.
This adds 'pretty-expanded' to a bunch of test cases that still work.

This commit shreds all remnants of libextra from the compiler and standard
distribution. Two modules, c_vec/tempfile, were moved into libstd after some
cleanup, and the other modules were moved to separate crates as seen fit.

Closes #8784
Closes #12413
Closes #12576

This was previously implemented, and it just needed a snapshot to go through

this will address the (crashing) new test added.