[exporter/datasetexporter]: Mark as alpha

[martin-majlis-s1]

Description: Change status to alpha

Based on the instructions - the last step should be:

• ✅ marking the component as Alfa - this is what I have done in this PR
• ✅ updating cmd/otelcontribcol/components.go - but this is what I have already done in the first PR [exporter/datasetexporter]: Initial Commit #20733 - and I can see, that it's still there.

Previous PRs:

• First PR: [exporter/datasetexporter]: Initial Commit #20733
• Second PR: [exporter/datasetexporter]: Initial implementation of logs and traces #21815

Link to tracking Issue: #20660

Testing:

• we are running this version for few weeks on our dev environments
• we are running open telemetry demo with our custom build image
• based on my initial benchmark it can export on my notebook around 2MB of logs per second

Documentation:

There are no updates in the documentation - it has still the same configuration.

[martin-majlis-s1]

@mx-psi : Since you have been reviewing, approving and merging previous PRs, could you, please, take a look on this PR?

[mx-psi]

LGTM, will wait for @atoulme to have a look as well on this one