Fix #54047

(I may have accidentally added it to some auxilliary crates as well;
my emacs-macro-based methodology was pretty crude.)

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

Additionally, add lots of tests for new functionality around statics and
`static mut`.

* The select/plural methods from format strings are removed
* The # character no longer needs to be escaped
* The \-based escapes have been removed
* '{{' is now an escape for '{'
* '}}' is now an escape for '}'

Closes #14810
[breaking-change]

Also remove all instances of 'self within the codebase.

This fixes #10889.

are currently inferred.  New rules are coming that will require
them to be explicit.  All add some explicit self declarations.

Except the pipes tests (that needs a snapshot)