fix: Resolve deadlock due to leaking in Connector recv drop

[orlp]

This fixes a bug that made values in the Connector channel leak if the receiver was dropped before the value was received.

In the receiver drop it now:

1. Prevents a new value from entering the channel.
2. Eagerly drops the value if there's still a value in the channel.
3. Wakes the sender.

The reason this resolves a deadlock is because we were sending WaitTokens that we rely on dropping through the channel. If those aren't dropped the associated WaitGroup will never unblock.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.89%. Comparing base (7f0bfa1) to head (c54255a).
Report is 13 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #21296      +/-   ##
==========================================
+ Coverage   79.80%   79.89%   +0.09%     
==========================================
  Files        1596     1596              
  Lines      228475   228562      +87     
  Branches     2607     2608       +1     
==========================================
+ Hits       182335   182613     +278     
+ Misses      45544    45353     -191     
  Partials      596      596              

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