[processor/metricsgeneration] Remove processor's experimental_ prefix in name

[crobert-1]

Component(s)

processor/metricsgeneration

Describe the issue you're reporting

This processor was first introduced to the contrib distribution in #3266, more than 3 years ago. It is considered alpha, and has been a part of contrib releases since at least v0.41.0. I think it's safe to remove the experimental_ prefix, and simply call it the metricsgeneration processor.

Please let me know if there's any reason we should leave it as-is. I realize renaming components is a breaking change, but as it's a simple rename it should be relatively simple to handle for users.

[github-actions]

Pinging code owners:

• processor/metricsgeneration: @Aneurysm9

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