Make compression negotiation more lenient

Unacceptable offers are declined without rejecting the request.

Closes #367

Closes #349

Closes #341

Closes #297

Returns real remote and local address instead mocked

Extend DialOptions to allow Host header override

Closes #315

The library we're currently using for protobufs is deprecated. Doesn't belong in the library core
anyway.

Closes #311
Updates #297

Fix dial panic when ctx is nil

Use net.ErrClosed

Go 1.16 has introduced net.ErrClosed, which should be returned/wrapped when an
I/O call is performed on a network connection which has already been closed.
This is useful to avoid cluttering logs with messages like "failed to close
WebSocket: already wrote close".

Closes: https://github.com/nhooyr/websocket/issues/286

Migrate from deprecated `io/ioutil`

Fixes https://github.com/nhooyr/websocket/issues/359

Credits to @maggie44 for making me add staticcheck.
See #407

Co-authored-by: maggie0002 <64841595+maggie0002@users.noreply.github.com>