Enable move semantics for socket types

[ChrisThrasher]

Description

This one wasn't entirely trivial because I had to write custom move operations for sf::Socket to ensure that a socket isn't closed after it's moved-from. The move operations ensure that the moved-from socket is given an invalid socket handle so that when close is called nothing happens. Enabling move semantics for sf::Socket had the downstream affect of enabling move semantics for 3 different derived classes. It's great how the type trait tests so easily detect and confirm that fact.

As a prerequisite I wrote up some sf::Socket tests since this class was lacking any.

[codecov]

Codecov Report

Merging #2658 (95b0e5e) into master (bbb6f60) will increase coverage by 0.06%.
The diff coverage is 93.33%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2658      +/-   ##
==========================================
+ Coverage   30.68%   30.74%   +0.06%     
==========================================
  Files         229      229              
  Lines       19718    19733      +15     
  Branches     4725     4728       +3     
==========================================
+ Hits         6050     6067      +17     
- Misses      12915    13045     +130     
+ Partials      753      621     -132     

Files Changed	Coverage Δ
include/SFML/Network/Socket.hpp	50.00% <ø> (ø)
src/SFML/Network/Socket.cpp	85.33% <93.33%> (+7.00%)	⬆️

... and 53 files with indirect coverage changes

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[Rosme]

That looks good to me.

[kimci86]

Nitpicking. Otherwise it looks correct.

[ChrisThrasher]

I included the Clang CI fix in this PR because other CI is guaranteed to fail. See #2661 for more information.

[kimci86]

I included the Clang CI fix in this PR because

You can edit this PR base branch to clang_ci_workaround to make the changes more specific. It will become master again automatically once clang_ci_workaround gets merged.

[ChrisThrasher]

I removed the CI failure workarounds from this PR since it appears that GitHub has fixed the issues.