feat: orbit metadata

[nstarman]

Add some read-only metadata to Orbit and MockStream. I'm not 100% sure what metadata we want, just that something seems useful.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 93.44%. Comparing base (63fe972) to head (7483ad2).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #259      +/-   ##
==========================================
+ Coverage   93.32%   93.44%   +0.11%     
==========================================
  Files          55       55              
  Lines        1993     2014      +21     
==========================================
+ Hits         1860     1882      +22     
+ Misses        133      132       -1     

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[nstarman]

I've been seeing some issues with tracer leakage in this PR! Need to figure out how to prevent that, otherwise this is a no-go for the current selection of MetaData.