Add OS-dependent reuse-port helpers

[rg0now]

Description

Enables listening on and dialing from the same UDP/TCP port. May set the following sockopts: SO_REUSEADDR and SO_REUSEPORT (required on Unix/Linux). Currently only Unix and Windows are supported.

Reference issue

Related pion/turn#514

[codecov]

Codecov Report

❌ Patch coverage is 66.66667% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.05%. Comparing base (5ae6667) to head (0943fa9).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
reuseport/control_unix.go	66.66%	1 Missing and 1 partial ⚠️

❌ Your patch status has failed because the patch coverage (66.66%) is below the target coverage (70.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #372      +/-   ##
==========================================
- Coverage   84.37%   84.05%   -0.32%     
==========================================
  Files          40       41       +1     
  Lines        3143     3149       +6     
==========================================
- Hits         2652     2647       -5     
- Misses        354      361       +7     
- Partials      137      141       +4     

Flag	Coverage Δ
go	84.05% <66.66%> (-0.32%)	⬇️

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