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

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

✅ 1266 untouched benchmarks

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_{Comparing rk/sparkstats (4d9b080) with develop (126c431)}