ARROW-7367: [Python] Use np.full instead of np.array.repeat in ParquetDatasetPiece
ARROW-7367: [Python] Use np.full instead of np.array.repeat in ParquetDatasetPiece

For small tables (len < 100) execution time is slightly degraded (~ x1.4 at len = 10), for large ones performance gain is huge (~ x0.04 at len = 100_000)

Closes #5999 from 0x0L/patch-1 and squashes the following commits:

1a9297dca <Xavier Lacroze> use np.full instead of np.array().repeat()

Authored-by: Xavier Lacroze <67e4fd0612f594c0fee184ac04c5356ac6258800@users.noreply.github.com>
Signed-off-by: Wes McKinney <3be70eed0275ec2606f002bff3514252e145d204@apache.org>

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