[Variant] Add nullable arg to StructArrayBuilder::with_field

[scovich]

Which issue does this PR close?

We generally require a GitHub issue to be filed for all bug fixes and enhancements and this helps us generate change logs for our releases. You can link an issue to this PR using the GitHub syntax.

• Closes #NNN.

Rationale for this change

StructArrayBuilder::with_field is currently hard-wired to assume the field will be nullable. This is unhelpful when adding non-nullable fields such as variant a metadata column.

What changes are included in this PR?

Add a third parameter, nullable.

Are these changes tested?

The builder is heavily used by unit tests, which have been adjusted to pass the new param.

Are there any user-facing changes?

No.

[scovich]

CC @alamb @codephage2020 -- should be a quickie

[alamb]

looks good to me -- thanks @scovich

[alamb]

It looks like there is a conflict in this PR

[scovich]

It looks like there is a conflict in this PR

Some kind of github confusion, methinks? The git cli handled it fine 🤷

arrow-rs % git merge oss/main
Auto-merging parquet-variant-compute/src/variant_get.rs
Merge made by the 'ort' strategy.
 parquet-variant-compute/src/lib.rs                                                     |  1 +
 parquet-variant-compute/src/{variant_get/mod.rs => variant_get.rs}                     | 10 ++++------
 parquet-variant-compute/src/variant_get/output/mod.rs                                  | 18 ------------------
 parquet-variant-compute/src/{variant_get/output/row_builder.rs => variant_to_arrow.rs} | 57 ++++++++++++++++++++++++++++++++-------------------------
 4 files changed, 37 insertions(+), 49 deletions(-)
 rename parquet-variant-compute/src/{variant_get/mod.rs => variant_get.rs} (99%)
 delete mode 100644 parquet-variant-compute/src/variant_get/output/mod.rs
 rename parquet-variant-compute/src/{variant_get/output/row_builder.rs => variant_to_arrow.rs} (73%)

[codephage2020]

looks good to me!

[alamb]

Merged up to resolve a conflict per @codephage2020

• [Variant] feat: Support typed_access for Boolean #8346 (comment)

[alamb]

Thanks @scovich and @codephage2020