Add arch test to detect usage of shared internal code

[jack-berg]

Related to #6970.

This test prints out instances of shared internal code use. We could eventually remove all the detected instances, at which point we could fail the build instead of just printing.

But there's a long way to go. See this gist for the current state of affairs.

Note: I don't currently have a good way to tell when internal code is referenced for things like the SDK's implementation of of opentelemetry-api-incubating, which is switched to a compile dependency in #6944.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.01%. Comparing base (a3d807b) to head (96f172a).
Report is 5 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #6978      +/-   ##
============================================
+ Coverage     89.99%   90.01%   +0.02%     
- Complexity     6601     6602       +1     
============================================
  Files           730      730              
  Lines         19864    19864              
  Branches       1956     1956              
============================================
+ Hits          17877    17881       +4     
+ Misses         1391     1389       -2     
+ Partials        596      594       -2     

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