Observability in library and statime linux

[cikzh]

This PR will add a Prometheus exporter, which will get its metrics from statime-linux via a Unix Domain Socket, very similar to how ntpd-rs does it.

It implements all currently available Instance datasets and exposes only a small set of metrics. The full exposure of metrics will be implemented in a separate PR

[codecov]

Codecov Report

Attention: 123 lines in your changes are missing coverage. Please review.

Comparison is base (8fd3820) 62.05% compared to head (f59e4db) 61.09%.
Report is 24 commits behind head on main.

❗ Current head f59e4db differs from pull request most recent head 8123fb3. Consider uploading reports for the commit 8123fb3 to get more accurate results

Files	Patch %	Lines
statime-linux/src/metrics/exporter.rs	0.00%	57 Missing ⚠️
statime/src/ptp_instance.rs	0.00%	21 Missing ⚠️
statime/src/observability/mod.rs	0.00%	14 Missing ⚠️
statime-linux/src/observer.rs	0.00%	11 Missing ⚠️
...tatime/src/datastructures/common/clock_identity.rs	0.00%	9 Missing ⚠️
statime-linux/src/main.rs	0.00%	7 Missing ⚠️
...tatime/src/datastructures/common/clock_accuracy.rs	50.00%	1 Missing ⚠️
statime/src/datastructures/common/clock_quality.rs	0.00%	1 Missing ⚠️
statime/src/datastructures/datasets/default.rs	0.00%	1 Missing ⚠️
statime/src/datastructures/messages/header.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #390      +/-   ##
==========================================
- Coverage   62.05%   61.09%   -0.97%     
==========================================
  Files          55       56       +1     
  Lines        6903     7012     +109     
==========================================
  Hits         4284     4284              
- Misses       2619     2728     +109     

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[davidv1992]

Note: Reverts #405 but I am fine with that as that did not fix the issue anyway.

[davidv1992]

Apologies, missed that sdoId still has the default serde deserializer, which is problematic as an sdo id should be below 2^12, which this doesn't enforce.