Is your feature request related to a problem or challenge? Please describe what you are trying to do.

• part of [EPIC] [Parquet] Implement Variant type support in Parquet #6736

The Variant encoding uses different sizes for offsets in nested types to optimize the encoding size

Specifically

• Objects use between 1-4 bytes for the field id depending on the number of fields
• Objects use between 1-4 bytes for the field offset depending on the size of the children

Describe the solution you'd like

I would like tests that use the VariantBuilder API and cover the following cases:

1. VariantObject with between 2^8 and 2^16 elements ( field_id_size_minus_1 = 1, 2 byte field ids)

2. VariantObject with between 2^16 and 2^24 elements ( field_id_size_minus_1 = 2, 3 byte field ids)

3. VariantObject with between 2^24 and 2^32 elements ( field_id_size_minus_1 = 3, 4 byte field ids)

4. VariantObject with total child data length between 2^8 and 2^16 elements ( field_offset_size_minus_1 = 1, 2 byte field offsets)

5. VariantObject with total child data length between 2^16 and 2^24 elements ( field_offset_size_minus_1 = 2, 3 byte field offsets)

6. VariantObject with total child data length between 2^24 and 2^32 elements ( field_offset_size_minus_1 = 3, 4 byte field offsets)

The "total child data length" can be made by adding some large strings as children (for example, by adding 1KB - 1MB Varaint::Strings via ArrayBuilder::append)

Describe alternatives you've considered

Additional context
The tests may not pass until this ticket is implemented:

• [Variant] Test and implement efficient building for "large" Arrays #7699

If they dont' pass, we can mark them #[ignored] until it is