Disable port sharing mechanisms when running in single processor mode

[ThadHouse]

Description

On linux, server sockets always enable SO_REUSEPORT. This has a side affect of not blocking other processes from accessing the port. If running in a single core execution context, we don't need to set SO_REUSEPORT, which allows that port blocking to work.

On windows, server sockets always are enabled with processor affinity. On single proc, this is likely not wanted, and similar behavior to client sockets are likely wanted.

Mac is already treated as single core, so no changes required.

Note that single core systems themselves are extremely rare nowadays, so this behavior is generally explicitly requested.

Testing

New test added to verify this behavior.

Documentation

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.89%. Comparing base (d5c2ac5) to head (5b23be7).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4528      +/-   ##
==========================================
- Coverage   86.25%   84.89%   -1.36%     
==========================================
  Files          56       56              
  Lines       15520    15520              
==========================================
- Hits        13386    13176     -210     
- Misses       2134     2344     +210     

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