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.

Long lines were fixed in a very crude way, as I'll be following up
with another reformat in a bit.

This changes the indexing syntax from .() to [], the vector syntax from ~[] to
[] and the extension syntax from #fmt() to #fmt[]

While it is still technically possible to test stage 0, it is not part of any
of the main testing rules and maintaining xfail-stage0 is a chore. Nobody
should worry about how tests fare in stage0.