Avoid peer timeout checks when there is no established connection

[davidsteiner]

• Changes the design so that we only store tokio Instants rather than pinned timer futures to simplify ownership logic
• Moves the peer timer into the active state to ensure it can only tick at appropriate times
• Moves the expected request ID for sent test requests into the active state

[codecov]

Codecov Report

❌ Patch coverage is 79.48718% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 63.56%. Comparing base (6a6f7e3) to head (80306fe).
⚠️ Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/hotfix/src/session.rs	38.46%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #134      +/-   ##
==========================================
+ Coverage   62.39%   63.56%   +1.17%     
==========================================
  Files          66       66              
  Lines        2760     2775      +15     
==========================================
+ Hits         1722     1764      +42     
+ Misses       1038     1011      -27     

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[DGPardo]

Very nice