The GenericStringBuilder should use GenericBinaryBuilder

[HaoYang670]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.
Currently, the string builder uses the list builder:

pub struct GenericStringBuilder<OffsetSize: OffsetSizeTrait> {
    builder: GenericListBuilder<OffsetSize, UInt8Builder>,
}

This requires another child array to be built, which leads to more memory overhead.

Describe the solution you'd like
I want the string builder to use the binary array.
Also I hope there would be some performance improvement in the bench_string. (At least, there should be no performance regression)

Describe alternatives you've considered
We could not do this if there is performance regression.

Additional context
Add any other context or screenshots about the feature request here.

[HaoYang670]

I will work on it.