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ARROW-6263: [Python] Use RecordBatch::Validate in RecordBatch.from_arrays. Normalize API vs. Table.from_arrays. Add record_batch factory function

It was previously possible to construct invalid RecordBatch objects. This also makes the API the same between Table.from_arrays and RecordBatch.from_arrays, where the latter did not have an explicit "schema" option before. A `pyarrow.record_batch` factory function has also been added to go alongside `pyarrow.table`

Closes #5189 from wesm/ARROW-6263 and squashes the following commits:

7514ea74a <Wes McKinney> Fix documentation
fd7172542 <Wes McKinney> Alphabetize
6c26f6424 <Wes McKinney> Validate schema against data in RecordBatch.from_arrays, normalize API, add record_batch factory function

Authored-by: Wes McKinney <wesm+git@apache.org>
Signed-off-by: Wes McKinney <wesm+git@apache.org>