arrow

ARROW-15332: [C++] Add new cases and fix issues in IPC read/write benchmark

 * The benchmark named ReadFile is misleading since it is actually reading from an in-memory buffer and no OS "read" call is ever issued.  I've renamed it to ReadBuffer (and ReadCompressedBuffer)
 * Renamed ReadTempFile to ReadCachedFile and added a second case for ReadUncachedFile. The former reads a file in the OS' page cache and the latter forces a read to actually hit the disk.
 * The TempFile benchmarks were not actually writing the correct amount of data and were reporting unrealistically high rates as a result.
 * Added a "partial read" parameter which, when true, only reads 1/8 the columns in the file so we can see the impact of pushdown projection.
 * Slightly reduced the range of parameters to keep the benchmark time reasonable (8k columns wasn't telling us anything more than 4k columns).

NOTE: This PR will invalidate some previous results from arrow-ipc-read-write-benchmark, disrupting conbench & other monitoring efforts.  This is because those previous results were wrong.

It also likely invalidates even more arrow-ipc-read-write-benchmark results because we added a new parameter and renamed some of the benchmarks.

Closes #12150 from westonpace/feature/ARROW-15332--add-fix-ipc-read-write-benchmark

Authored-by: Weston Pace <weston.pace@gmail.com>
Signed-off-by: Weston Pace <weston.pace@gmail.com>