[Variant] Tests for creating "large" `VariantList`s

[alamb]

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

• Arrays (VariantList) use 1 byte and 4 bytes for length when the list has <=256 and >256 list elements respectively
• Arrays (VariantList) use 1 byte and 4 bytes for the offset depending on how large the total variant payload size is

Describe the solution you'd like

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

1. VariantList with more than 256 elements
2. VariantList with total child data length between 2^8 and 2^16 ( field_offset_size_minus_1 = 1, 2 byte offsets)
3. VariantList with total child data length between 2^16 and 2^24 ( field_offset_size_minus_1 = 2, 3 byte offsets)
4. VariantList with total child data length between 2^24 and 2^32 ( field_offset_size_minus_1 = 3, 4 byte 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 ListBuilder::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

[klion26]

take

[alamb]

label_issue.py automatically added labels {'parquet'} from #7876