remote/coordinator: prohibit multiple exporters with the same name

[jluebbe]

Since the switch to gRPC, we only check that we don't have a connection from the same peer, but not with the same name, which would break assumptions elsewhere in the code and confuse users.

Fix it by raising an exception in this case and shutting down both sides of the ExporterStream.

Fixes: #1774

[codecov]

Codecov Report

❌ Patch coverage is 0% with 18 lines in your changes missing coverage. Please review.
✅ Project coverage is 45.1%. Comparing base (70f6150) to head (ac6362a).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
labgrid/remote/coordinator.py	0.0%	18 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           master   #1775     +/-   ##
========================================
- Coverage    45.2%   45.1%   -0.1%     
========================================
  Files         172     172             
  Lines       13569   13587     +18     
========================================
  Hits         6136    6136             
- Misses       7433    7451     +18     

Flag	Coverage Δ
3.10	45.1% <0.0%> (-0.1%)	⬇️
3.11	45.1% <0.0%> (-0.1%)	⬇️
3.12	45.1% <0.0%> (-0.1%)	⬇️
3.13	45.1% <0.0%> (-0.1%)	⬇️
3.14	45.1% <0.0%> (-0.1%)	⬇️
3.9	45.2% <0.0%> (-0.1%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

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

[jluebbe]

This introduces quite some complexity, but I've not found a simpler way to handle the different ordering startup can fail. A better way to wait for asyncio events directly and a simpler way for bidirectional gRPC communication would be nice.

[threexc]

Should this be remote/coordinator: prohibit multiple exporters with the same name ?