queue_size & queue_capacity gauges not available in otel metrics

[codeboten]

Describe the bug
The following metrics are not available via opentelemetry metrics:

otelcol_exporter_queue_capacity{exporter="otlp"} 1000
otelcol_exporter_queue_size{exporter="otlp"} 0

This is because they're registered with a separate registry than the one used by the otel OC bridge.

Steps to reproduce
Enabled the following feature gates:

--feature-gates=telemetry.useOtelForInternalMetrics
--feature-gates=telemetry.useOtelWithSDKConfigurationForInternalTelemetry

What did you expect to see?
Expected to see those metrics emitted via OTLP

What did you see instead?
Those metrics did not appear

What version did you use?
v0.87.0

[codeboten]

This is related to #8673 but I opened a separate issue since these are gauges and not counters