Using experimental OTEL API for removing metrics

[mariomac]

It replaces the current observable-based OTEL api for removing counters and gauges to a general-purpose experimental API that also allows removing Histograms: https://github.com/grafana/opentelemetry-go/tree/v1.27.0-grafana.1 (kudos to @pyohannes !).

Tasks:

• Update documentation.
• Testing histograms removal for the app metrics exporter.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 81.73077% with 38 lines in your changes missing coverage. Please review.

Project coverage is 72.16%. Comparing base (b73549b) to head (1a8f7f4).
Report is 1 commits behind head on main.

Files	Patch %	Lines
pkg/internal/export/otel/metrics_proc.go	82.85%	6 Missing and 6 partials ⚠️
pkg/internal/export/otel/expirer.go	69.23%	7 Missing and 1 partial ⚠️
pkg/internal/export/prom/prom_proc.go	50.00%	8 Missing ⚠️
pkg/internal/export/prom/prom.go	68.42%	6 Missing ⚠️
pkg/internal/export/otel/metrics_net.go	88.88%	1 Missing and 1 partial ⚠️
pkg/internal/export/expire/expiry_map.go	75.00%	1 Missing ⚠️
pkg/internal/export/prom/expirer.go	87.50%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #937      +/-   ##
==========================================
- Coverage   79.15%   72.16%   -7.00%     
==========================================
  Files         131      130       -1     
  Lines       10104    10110       +6     
==========================================
- Hits         7998     7296     -702     
- Misses       1597     2188     +591     
- Partials      509      626     +117     

Flag	Coverage Δ
integration-test	55.24% <68.75%> (-0.30%)	⬇️
k8s-integration-test	59.11% <75.00%> (-0.24%)	⬇️
oats-test	36.16% <26.44%> (+0.63%)	⬆️
unittests	?

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[grcevski]

LGTM! Excellent!