[chore][kafkaexporter] Add stability level per metric

[ChrsMark]

Description

open-telemetry/opentelemetry-collector#13756 added support for exposing metrics' stability level in the generated documentation. This PR makes use of this functionality.

We start by setting the stability of all metrics to development. More info about levels can be found at https://github.com/open-telemetry/opentelemetry-specification/blob/v1.49.0/oteps/0232-maturity-of-otel.md#maturity-levels.

Related to:

• Document SemConv compatibility requirements for components stability opentelemetry-collector#11878
• [mdatagen] Consider linking metrics/attributes from metadata.yaml to SemConv definitions opentelemetry-collector#13297
• [receiver/hostmetricsreceiver] semantic conventions transition #35325
• Add stability level per metric #42809

Link to tracking issue

Fixes ~

Testing

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Documentation

Updated

[axw]

Thanks! Some of these can probably be bumped above development, but we can handle that in a followup.