feat: Allow configuring a dedicated metrics logger

[edgarrmondragon]

Summary

New metrics helpers

The most important difference: the previous implementation only emitted total records at the end of sync, while the new one emits the accumulated record count between regular intervals (60s by default). This allows, among other things, to plot record counts against time for a child and parent stream:

Takes inspiration from singer-python. The new classes actually output time-series data for record count, sync duration and HTTP request duration.

The Point class

This dataclass has a custom __str__() method that renders the object as JSON, that means disabling metrics via log config (e.g. level ERROR) results in not needing to perform the costly object->string conversion and makes testing metrics easier by capturing the raw object from the LogRecord instance.

Logging configuration

Since metrics are just special logs, I think the best way to configure them is via generic log configuration. So, the SDK now supports an SINGER_SDK_LOG_CONFIG env var that points to a logging config file in YAML format (same as meltano).

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📚 Documentation preview 📚: https://meltano-sdk--978.org.readthedocs.build/en/978/

[codecov]

Codecov Report

Merging #978 (103a731) into main (3c8e213) will increase coverage by 0.81%.
The diff coverage is 93.50%.

❗ Current head 103a731 differs from pull request most recent head 7be243f. Consider uploading reports for the commit 7be243f to get more accurate results

@@            Coverage Diff             @@
##             main     #978      +/-   ##
==========================================
+ Coverage   82.18%   83.00%   +0.81%     
==========================================
  Files          37       39       +2     
  Lines        3621     3748     +127     
  Branches      625      629       +4     
==========================================
+ Hits         2976     3111     +135     
+ Misses        479      473       -6     
+ Partials      166      164       -2     

Impacted Files	Coverage Δ
singer_sdk/streams/core.py	85.30% <86.36%> (+2.16%)	⬆️
singer_sdk/streams/rest.py	84.90% <88.23%> (+1.24%)	⬆️
singer_sdk/metrics.py	96.03% <96.03%> (ø)
singer_sdk/helpers/_resources.py	100.00% <100.00%> (ø)
singer_sdk/plugin_base.py	75.14% <100.00%> (+0.43%)	⬆️

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[edgarrmondragon]

pre-commit.ci autofix

[aaronsteers]

Exciting!!

[cjohnhanson]

Looks good! 🚀