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PARQUET-2225: [C++][Parquet] Allow reading dense with RecordReader (#17877)

Currently ReadRecords reads spaced by default. Some readers may need to read the values dense, and reading spaced is less efficient than reading dense. We need an option for reading dense.

Lead-authored-by: Fatemah Panahi <panahi@google.com>
Co-authored-by: Fatemah Panahi <fatemehp@users.noreply.github.com>
Signed-off-by: Micah Kornfield <micahk@google.com>