Add SetExtensions, drop special raddr/rport/tcptype

[JoTurk]

Description

When I added extension parser a while ago ab6e243 (this parser was needed for webrtc to drop old generation candidates pion/webrtc#2993)

We had to keep special treatments and APIs for raddr and rport, we couldn't break the candidates API to wire them so webrtc has to parse extensions again https://github.com/pion/webrtc/blob/0272096d3d032d31c590eb63731fbb795c02785e/icecandidate.go#L147-L203

This adds SetExtensions, drops all the raddr, rport and tcptype special parsers and APIs.

[codecov]

Codecov Report

❌ Patch coverage is 93.47826% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.68%. Comparing base (4eeedad) to head (4ee08eb).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
candidate_base.go	95.74%	2 Missing ⚠️
candidate_host.go	50.00%	1 Missing ⚠️
candidate_peer_reflexive.go	50.00%	1 Missing ⚠️
candidate_relay.go	50.00%	1 Missing ⚠️
candidate_server_reflexive.go	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1022      +/-   ##
==========================================
- Coverage   91.90%   91.68%   -0.22%     
==========================================
  Files          46       45       -1     
  Lines        5536     5439      -97     
==========================================
- Hits         5088     4987     -101     
- Misses        448      452       +4     

Flag	Coverage Δ
go	91.68% <93.47%> (-0.22%)	⬇️

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