Update storage metrics to beta

[LoginovIlia]

What type of PR is this?

/kind feature

What this PR does / why we need it:

1. Updated to BETA stability:

• apiserver_storage_transformation_duration_seconds
• apiserver_storage_transformation_operations_total
• apiserver_storage_envelope_transformation_cache_misses_total
• apiserver_storage_data_key_generation_duration_seconds
• apiserver_storage_data_key_generation_failures_total

2. Updated unit tests for that metrics
3. Updated the documentation and testdata.

Which issue(s) this PR is related to:

Part of #136304

Special notes for your reviewer:

Does this PR introduce a user-facing change?

Promote the apiserver storage 'apiserver_storage_transformation_duration_seconds', 'apiserver_storage_transformation_operations_total', 'apiserver_storage_envelope_transformation_cache_misses_total', 'apiserver_storage_data_key_generation_duration_seconds', and 'apiserver_storage_data_key_generation_failures_total' metrics to BETA and update their documentation

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

[k8s-ci-robot]

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If a SIG or subproject determines this is a relevant issue, they will accept it by applying the triage/accepted label and provide further guidance.

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[k8s-ci-robot]

Hi @LoginovIlia. Thanks for your PR.

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[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: LoginovIlia
Once this PR has been reviewed and has the lgtm label, please assign dashpole, smarterclayton for approval. For more information see the Code Review Process.

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Details

Needs approval from an approver in each of these files:

• staging/src/k8s.io/apiserver/pkg/storage/value/OWNERS
• test/instrumentation/OWNERS
• test/instrumentation/testdata/OWNERS

Approvers can indicate their approval by writing /approve in a comment
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[k8s-triage-robot]

This PR may require stable metrics review.

Stable metrics are guaranteed to not change. Please review the documentation for the requirements and lifecycle of stable metrics and ensure that your metrics meet these guidelines.

[tico88612]

Hi, I already opened for this #137031