Handle stale nonces in ChannelBind, and add timer to renew bindings

[berkant]

Description

While the issue was originally about discussing why turn would fall back to indications after a while in a long-lived connection, tracing down into the code revealed stale nonces aren't being handled whatsoever by the bind() method, causing channel bindings to time out and transition to failed state, forcing the connection to go 2-way over indications for the rest of its life.

This PR adds code handling stale nonce errors to ChannelBind requests. It also decouples logic related to binding lifecycle (initial binding & binding renewal) from WriteTo by carving out code into a timer, similar to the way perms and allocs work.

Reference issue

Fixes #471

[codecov]

Codecov Report

❌ Patch coverage is 91.66667% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 71.26%. Comparing base (55f84c2) to head (005a1d6).
⚠️ Report is 3 commits behind head on master.

Files with missing lines	Patch %	Lines
internal/client/udp_conn.go	89.47%	3 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #481      +/-   ##
==========================================
+ Coverage   68.54%   71.26%   +2.71%     
==========================================
  Files          45       45              
  Lines        3300     2624     -676     
==========================================
- Hits         2262     1870     -392     
+ Misses        865      581     -284     
  Partials      173      173              

Flag	Coverage Δ
go	71.26% <91.66%> (+2.71%)	⬆️
wasm	?

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[berkant]

@JoeTurki WDYT?

[JoeTurki]

@berkant Thank you so much, I like this change, I'll review it again in details either tonight or this weekend.