Support reporting statistics in spark datasource

[robert3005]

Spark mostly focuses on sizeInBytes which we populate from file sizes with
scaling. We also report numRows since that exists in our datasource.

[codspeed-hq]

Merging this PR will not alter performance

✅ 207 untouched benchmarks
⏩ 1044 skipped benchmarks¹

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_{Comparing rk/sparkstats (6da0126) with develop (581e9dd)}

Footnotes

1. 1044 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩