network: Use peer address after proxy fix for app rate limiter if available

[algorandskiy]

Summary

peer.RoutingAddr used to use conn.Addr to get remote IP. Changed to use remoteAddress in order to accommodate possible reverse proxy hiding nodes behind.

Additionally, changed X-Forwarded-For handing to allow the single reverse proxy use case (handle potentially adversarial "X-Forwared-For" headers from clients).
Before: did not use any values if there is a list of values in the first X-Forwarded-For header.
After: use the last value in the list "A, B, C" in the last X-Forwarded-For header.

Test Plan

Added a test ws proxy implementation and a unit test checking the addr is taken from a proxy-provided header.
Added unit tests for X-Forwarded-For and RoutingAddr changes.

[codecov]

Codecov Report

Attention: 8 lines in your changes are missing coverage. Please review.

Comparison is base (3abe5c8) 55.83% compared to head (9b70c0f) 29.16%.
Report is 3 commits behind head on master.

Files	Patch %	Lines
network/wsPeer.go	0.00%	5 Missing ⚠️
network/requestTracker.go	78.57%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #5848       +/-   ##
===========================================
- Coverage   55.83%   29.16%   -26.67%     
===========================================
  Files         477      477               
  Lines       67256    67269       +13     
===========================================
- Hits        37552    19621    -17931     
- Misses      27171    45590    +18419     
+ Partials     2533     2058      -475     

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

[jannotti]

I have a lot more to read, but need to stop early for the day.

[gmalouf]

Easy to follow, feedback incorporated well. Agree with decision to apply the last in list rule solely X-Forwarded-For.