all: remove u-module naming where possible

[dpgeorge]

This changes almost all uses of "u-module" to just "module" for the following built-in modules:

• asyncio
• binascii
• collections
• errno
• io
• json
• socket
• struct
• sys
• time

There are some remaining uses of "u-module" naming, for the cases where the built-in module is extended in Python, eg python-stdlib/os uses uos.

Also, there are remaining uses of utime when non-standard (compared to CPython) functions are used, like utime.ticks_ms().