Create placeholder for meter_provider declarative configuration

[mariomac]

In preparation for #903:

• Create a base meter_provider configuration to progressively add support for OTEL declarative configuration in the future.
• Move otel_metric_export > features to a common meter_provider > features, and deprecate it
• Move prometheus > features to meter_provider > features, and deprecate it
• Handle new configuration from integration tests
• Update documentation --> Will submit a pr to opentelemetry.io docs as soon as the new format is accepted/agreed.

The reason to move the features specification to a common section is because in the next PRs, we will allow a declarative per-service metric features definition. Having different metric features per export endpoint adds a lot of complexity to the code.

[codecov]

Codecov Report

❌ Patch coverage is 68.71166% with 51 lines in your changes missing coverage. Please review.
✅ Project coverage is 56.32%. Comparing base (b4c3b17) to head (257f060).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/export/prom/prom.go	17.14%	22 Missing and 7 partials ⚠️
pkg/export/otel/metrics.go	73.91%	0 Missing and 6 partials ⚠️
pkg/export/prom/prom_bpf.go	50.00%	5 Missing ⚠️
pkg/instrumenter/instrumenter_test_linux.go	0.00%	4 Missing ⚠️
pkg/obi/config.go	86.36%	0 Missing and 3 partials ⚠️
pkg/export/feature.go	95.12%	2 Missing ⚠️
pkg/export/prom/prom_net.go	66.66%	0 Missing and 1 partial ⚠️
pkg/internal/otelsdk/sdk_inject.go	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #943      +/-   ##
==========================================
+ Coverage   47.13%   56.32%   +9.18%     
==========================================
  Files         255      255              
  Lines       22139    22142       +3     
==========================================
+ Hits        10436    12472    +2036     
+ Misses      11041     8825    -2216     
- Partials      662      845     +183     

Flag	Coverage Δ
integration-test	22.92% <42.33%> (?)
integration-test-arm	0.00% <0.00%> (?)
integration-test-vm-${ARCH}-${KERNEL_VERSION}	0.00% <0.00%> (?)
k8s-integration-test	2.68% <0.00%> (?)
oats-test	0.00% <0.00%> (?)
unittests	47.70% <68.09%> (+0.56%)	⬆️

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[grcevski]

why do we call them obi_features, instead of features?