fix(urls): standardize pass-through of parsed query parameters

[cpcloud]

This PR cleans up our URL handling a bit.

1. We were doing a bunch of unnecessary url parse -> url unparse, only to
   immediately again parse the URL as the first call in every _from_url
   implementation.
2. Each backend was separately handling converting query parameters to single
   scalars where possible, due to the unparsing
3. Query parameters were sometimes passed into kwargs and sometimes parsed
   again to then be used as kwargs later

So, I did the following:

1. Pass the ParseResult into the _from_url implementation.
2. Convert query parameters into single values where possible before calling backend._from_url
3. Pass all query parameters as **kwargs into the _from_url call.

Fixes #9456.

[gforsyth]

Do we want to get #9466 in first?

[cpcloud]

Do we want to get #9466 in first?

Yep.

Is that waiting on anything?

[cpcloud]

Merged #9466 and rebased this PR on main. Hopefully just waiting on CI at this point!

[gforsyth]

noice!