Deprecate top-level service selection

[marctc]

This PR removes top-level service selection from the docs and marks the fields as deprecated.
Beyla still would be able to be configured that we want to keep deprecated/undocumented.

Fixes #1684
Fixes #1206

[grafsean]

Thanks @marctc and does this need to be back ported to 2.0 or is this for a future release?

[marctc]

Thanks @marctc and does this need to be back ported to 2.0 or is this for a future release?

I think this probably good for Beyla 2.1. I don't think we should backport it

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 65.25%. Comparing base (cf94133) to head (bc7cff2).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1768      +/-   ##
==========================================
- Coverage   67.00%   65.25%   -1.76%     
==========================================
  Files         219      203      -16     
  Lines       22691    20890    -1801     
==========================================
- Hits        15205    13631    -1574     
+ Misses       6714     6378     -336     
- Partials      772      881     +109     

Flag	Coverage Δ
integration-test	54.52% <ø> (-0.32%)	⬇️
k8s-integration-test	53.03% <ø> (+<0.01%)	⬆️
oats-test	34.32% <ø> (+0.02%)	⬆️
unittests	?

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