Overhaul stats: Refactor metrics (part 1)

[josecelano]

Refactor metrics (part 1)

Subtasks

• Extract macro for metric name constructor (to fail at compilation time with empty names)
• Replace metric name constructor by new macro
• Extract macro for label name constructor (to fail at compilation time with empty names)
• Replace label name constructor by new macro
• Return an optional in get_counter_value and get_gauge_value.
• Return errors instead of panicking in the MetricCollection struct.
• Add logs to the listener's initialization (when it starts and finishes).
• Add req kind label to the number of errors metric.
• Add tracing crate.

[codecov]

Codecov Report

Attention: Patch coverage is 90.04149% with 48 lines in your changes missing coverage. Please review.

Project coverage is 84.41%. Comparing base (b061357) to head (f9ad729).
Report is 13 commits behind head on develop.

Files with missing lines	Patch %	Lines
packages/metrics/src/metric_collection.rs	95.45%	4 Missing and 5 partials ⚠️
...udp-tracker-server/src/statistics/event/handler.rs	84.74%	9 Missing ⚠️
...ckages/http-tracker-core/src/statistics/metrics.rs	46.66%	8 Missing ⚠️
...ackages/udp-tracker-core/src/statistics/metrics.rs	46.66%	8 Missing ⚠️
packages/metrics/src/label/value.rs	0.00%	3 Missing ⚠️
...s/udp-tracker-core/src/statistics/event/handler.rs	85.71%	3 Missing ⚠️
.../http-tracker-core/src/statistics/event/handler.rs	85.71%	2 Missing ⚠️
...ackages/http-tracker-core/src/statistics/keeper.rs	60.00%	0 Missing and 2 partials ⚠️
packages/udp-tracker-core/src/statistics/keeper.rs	60.00%	0 Missing and 2 partials ⚠️
...ckages/udp-tracker-server/src/statistics/keeper.rs	60.00%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1467      +/-   ##
===========================================
- Coverage    84.66%   84.41%   -0.26%     
===========================================
  Files          254      254              
  Lines        19160    19337     +177     
  Branches     19160    19337     +177     
===========================================
+ Hits         16222    16323     +101     
- Misses        2675     2737      +62     
- Partials       263      277      +14     

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[josecelano]

ACK f9ad729