ref(otel): Remove autoinstrumentation

[sentrivana]

Removing experimental OTel autoinstrumentation since we want to focus on getting basic OTel support right. Once we're confident that our instrumentation works correctly with OTel, we can focus on adding OTel integration packages.

We can reuse some stuff this PR removes then, if necessary.

I've kept the basic skeleton and an example with Django for later to have it in place once we start enabling integrations one by one.

Closes #3238

[codecov]

Codecov Report

Attention: Patch coverage is 65.00000% with 7 lines in your changes missing coverage. Please review.

Project coverage is 79.72%. Comparing base (6bb2081) to head (08df6aa).

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3239      +/-   ##
==========================================
- Coverage   79.76%   79.72%   -0.05%     
==========================================
  Files         133      132       -1     
  Lines       14313    14237      -76     
  Branches     3012     2997      -15     
==========================================
- Hits        11417    11350      -67     
+ Misses       2074     2065       -9     
  Partials      822      822              

Files	Coverage Δ
...ntry_sdk/integrations/opentelemetry/integration.py	63.33% <65.00%> (-13.48%)	⬇️

... and 3 files with indirect coverage changes

[sl0thentr0py]

didn't we want to keep the distro setup for later?

[sentrivana]

didn't we want to keep the distro setup for later?

The distro setup mostly makes sense if we're using OTel's autodiscovery of instrumentation packages. But since we now want to enable integrations one by one explicitly, we can get rid of the distro stuff. (It also wasn't a "real" distro in the sense of how it should be used. So all in all better to get rid of it to not confuse people.)