Enable tracing in the a3m gRPC client

[sevein]

Enable OpenTelemetry tracing in the gRPC client and create it from main following recommended practices. I've also added a small test for the a3m activity, but it's improvable.

After checking out the traces in Grafana I realized that we were sending hundreds of Read requests to a3m so I've also introduced a small wait between reads to reduce the frequency.

[codecov]

Codecov Report

Attention: Patch coverage is 43.47826% with 13 lines in your changes are missing coverage. Please review.

Project coverage is 48.17%. Comparing base (9f4a60a) to head (32ae4fb).
Report is 1 commits behind head on main.

Files	Patch %	Lines
cmd/enduro-a3m-worker/main.go	0.00%	6 Missing ⚠️
internal/a3m/client.go	0.00%	6 Missing ⚠️
internal/a3m/a3m.go	90.90%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #905      +/-   ##
==========================================
+ Coverage   46.83%   48.17%   +1.33%     
==========================================
  Files         103      103              
  Lines        5549     5555       +6     
==========================================
+ Hits         2599     2676      +77     
+ Misses       2713     2636      -77     
- Partials      237      243       +6     

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[djjuhasz]

One nitpick, but it's not a blocker. 👍