[API] Allowed always setting an option to current or default value

[ethouris]

Changes:

1. Every option should be able to be set to the default value.
2. Setting the current value should be always accepted without verification.
3. Some fixes in the documentation for socket options.

[codecov]

Codecov Report

❌ Patch coverage is 33.33333% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 61.77%. Comparing base (0976f76) to head (2bb63bf).
⚠️ Report is 54 commits behind head on master.

Files with missing lines	Patch %	Lines
srtcore/socketconfig.cpp	33.33%	6 Missing and 4 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3374      +/-   ##
==========================================
- Coverage   67.88%   61.77%   -6.11%     
==========================================
  Files         101      103       +2     
  Lines       18489    19879    +1390     
  Branches        0     2936    +2936     
==========================================
- Hits        12551    12280     -271     
- Misses       5938     6310     +372     
- Partials        0     1289    +1289     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.