feat: metrics system overhaul

[eledhwen]

Overhauls the metrics system by:

• decoupling marker / label management (new MarkerManager component) from micrometer Meter management (new Metrics component)
• making it so MarkerManager can be injected into components in order to annotate custom metrics
• clarifying some method signatures, notably in order to make LocalContext more explicit

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 94.76190% with 11 lines in your changes missing coverage. Please review.

Project coverage is 82.31%. Comparing base (ba47e03) to head (1018dc3).
Report is 3 commits behind head on master.

Files with missing lines	Patch %	Lines
...ver/mapper_factory/MarkerManagerMapperFactory.java	71.42%	1 Missing and 1 partial ⚠️
...per_factory/ObservabilityManagerMapperFactory.java	71.42%	1 Missing and 1 partial ⚠️
...ne/input/initializer/runner/InitializerRunner.java	71.42%	2 Missing ⚠️
...a/tech/illuin/pipeline/sink/runner/SinkRunner.java	77.77%	2 Missing ⚠️
...a/tech/illuin/pipeline/step/runner/StepRunner.java	75.00%	2 Missing ⚠️
...ipeline/execution/phase/impl/InitializerPhase.java	85.71%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #144      +/-   ##
============================================
+ Coverage     82.10%   82.31%   +0.20%     
- Complexity      779      789      +10     
============================================
  Files           140      147       +7     
  Lines          2079     2098      +19     
  Branches        120      120              
============================================
+ Hits           1707     1727      +20     
- Misses          290      291       +1     
+ Partials         82       80       -2     

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