Add support for NumPy arrays to the arrow serializer for string datatypes

[abey79]

What

This adds support for Numpy array for batches of Utf8 datatypes. For example, this facilitates logging a TextBatch when using Pandas dataframe:

rr.send_columns(
    "/entity/path",
    times=[rr.TimeSequenceColumn("frame_nr", df["frame_nr"])],
    components=[
        rr.components.TextBatch(np.where(df["mouth_open"], "OPEN", "CLOSE")),
    ],
)

Checklist

• I have read and agree to Contributor Guide and the Code of Conduct
• I've included a screenshot or gif (if applicable)
• I have tested the web demo (if applicable):
  • Using examples from latest main build: rerun.io/viewer
  • Using full set of examples from nightly build: rerun.io/viewer
• The PR title and labels are set such as to maximize their usefulness for the next release's CHANGELOG
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• If have noted any breaking changes to the log API in CHANGELOG.md and the migration guide

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[Wumpf]

unit test plz!

also this could be fairly easy part of codegen? Something seems to be wrong with codegen here