Add validated row decode benchmark

[alamb]

Which issue does this PR close?

• related to Validate short view strings in separate buffer in arrow-row #10250 from @Jefffrey

Rationale for this change

The existing row format benchmark measures convert_rows using rows created directly by RowConverter::convert_columns, which skips UTF-8 validation during decode.

What changes are included in this PR?

This adds a convert_rows_validated benchmark that decodes rows parsed through RowParser, exercising the UTF-8 validation path. It also derives Clone for Rows so the benchmark setup can reuse the prepared rows when converting to binary.

Are these changes tested?

CI.

I also ran it locally like

cargo bench --bench row_format -- convert_rows_validated

Are there any user-facing changes?

No breaking changes. Rows now implements Clone.

[alamb]

I profiled these benchmarks locally and the profile looks reasonable to me (it is validating the parsed rows)

[Jefffrey]

this is a good catch; didn't realize we needed this roundabout way of enabling validation

one concern i have here is this will add this new bench for non-string types creating more benchmark noise (and i think it ignores nulls too so the null config benches also get extra noise because of this)

probably want to config this so it only runs for string types (and probably just for the 0.0 null density case) 🤔

[Jefffrey]

does this mean nulls are ignored in this bench?

[alamb]

Good call -- I fixed that by not converting into binary first

[alamb]

this is a good catch; didn't realize we needed this roundabout way of enabling validation

Yeah -- it took me a while too -- I think the idea is that Rows are assumed to be valid when prodiced by a row converter. It is only when they may have come from somewhere else (e.g. a spill file) they need to be validated

one concern i have here is this will add this new bench for non-string types creating more benchmark noise (and i think it ignores nulls too so the null config benches also get extra noise because of this)

[Jefffrey]

thanks @alamb