refactor: First migration attempt from requests to httpx.

[bvanelli]

There are a couple of reasons to do this:

• requests is in maintanance mode, and doesn't really support modern things like http2
• For me, the first resolution is much faster, possibly because requests needs a lot more time to establish a first connection. I believe this only affects IPV6 resolution with DuckDNS. Performance seems to be similar with other benchmarks I ran.
• httpx can support asyncio in the future, if I can think of a good enough integration (straight forward support for both sync and async).
• httpx seems to be one of the more modern and stable libraries out there.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.01%. Comparing base (cb6eb96) to head (aa71944).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #187      +/-   ##
==========================================
+ Coverage   97.94%   98.01%   +0.07%     
==========================================
  Files          21       21              
  Lines        3117     3131      +14     
==========================================
+ Hits         3053     3069      +16     
+ Misses         64       62       -2     

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