Allow empty hosts for schemes that do not require them

[bdraco]

What do these changes do?

Allow empty hosts for schemes that do not require them

Are there changes in behavior for the user?

schemes other than "http", "https", "ws", "wss", "ftp" will not raise ValueError on empty host anymore

Related issue number

fixes #821

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.39%. Comparing base (07c4e03) to head (bc68be6).
Report is 278 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1136      +/-   ##
==========================================
+ Coverage   95.20%   95.39%   +0.19%     
==========================================
  Files          30       30              
  Lines        4709     4733      +24     
  Branches      417      420       +3     
==========================================
+ Hits         4483     4515      +32     
+ Misses        200      192       -8     
  Partials       26       26              

Flag	Coverage Δ
CI-GHA	95.35% <100.00%> (+0.19%)	⬆️
MyPy	40.89% <52.63%> (+0.11%)	⬆️
OS-Linux	99.39% <100.00%> (+<0.01%)	⬆️
OS-Windows	99.49% <100.00%> (+<0.01%)	⬆️
OS-macOS	99.10% <100.00%> (+<0.01%)	⬆️
Py-3.10.11	99.00% <100.00%> (+<0.01%)	⬆️
Py-3.10.14	99.23% <100.00%> (+<0.01%)	⬆️
Py-3.11.9	99.23% <100.00%> (+<0.01%)	⬆️
Py-3.12.5	99.23% <100.00%> (+<0.01%)	⬆️
Py-3.13.0-rc.1	99.23% <100.00%> (+<0.01%)	⬆️
Py-3.8.10	98.94% <100.00%> (+<0.01%)	⬆️
Py-3.8.18	99.18% <100.00%> (+<0.01%)	⬆️
Py-3.9.13	98.94% <100.00%> (+<0.01%)	⬆️
Py-3.9.19	99.18% <100.00%> (+<0.01%)	⬆️
Py-pypy7.3.11	99.24% <100.00%> (+<0.01%)	⬆️
Py-pypy7.3.16	99.23% <100.00%> (+<0.01%)	⬆️
Py-pypy7.3.17	99.26% <100.00%> (+<0.01%)	⬆️
VM-macos-latest	99.10% <100.00%> (+<0.01%)	⬆️
VM-ubuntu-latest	99.39% <100.00%> (+<0.01%)	⬆️
VM-windows-latest	99.49% <100.00%> (+<0.01%)	⬆️
pytest	99.39% <100.00%> (+<0.01%)	⬆️

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