We don’t use the Tests library target anyway.

And move it to the RxLibrary.

Tiny typo plus addition of URI RFC reference and formatting.

Removed compression levels from clients and _experimental_'d signature of methods manipulating compression algorithms

With GRXWriter a subclass of all writers, we can map the requestsWriter directly
without a dumb wrapper, and return GRXImmediateWriter objects where GRXWriter is
expected.