Add extend/extend_unchecked for MutableUtf8Array

[VasanthakumarV]

This PR adds TrustedLen-based extend and extend_unchecked methods for MutableUtf8Array.

[VasanthakumarV]

@jorgecarleitao I started working on MutableUtf8Array, it passes a simple test case.

Will you be able to look at the code, and suggest changes, just to make sure I am on the correct track.

[jorgecarleitao]

Thanks for picking this up! This is a great start!

Two notes: if we use a vector, we will need to double-allocate: one for the vector, one for the self.values. The goal is to extend the self.values directly.

An idea: create a new function (not method) fn unsafe extend_from_trusted_len_iter_values and modify trusted_len_values_iter to become something like

fn unsafe trusted_len_values_iter(iterator) {
    /// initialize the state 
    let capacity = iterator.size_hint().1.unwrap();
    let mut offsets = MutableBuffer::with_capacity(capacity + 1);
    offsets.push(O::default());
    let mut values = MutableBuffer::new();
    extend_from_trusted_len_iter_values(&mut offsets, &mut values, iterator);
    (offsets, values)
}

then, move the for loop logic currently in trusted_len_values_iter to extend_from_trusted_len_iter_values. This way, both creation and extension use the same code based (in extend_from_trusted_len_iter_values).

The same ideas can be applied to the one with the validity.

[VasanthakumarV]

@jorgecarleitao Now,

• extend_trusted_len_values and from_trusted_len_values_iter share extend_from_trusted_len_values_iter
• extend_trusted_len and from_trusted_len_iter share extend_from_trusted_len_iter

If you can review once more, and provide feedback, I will feel more confident working on the others independently, and hopefully disturb you less often.

PS: All of the existing tests and new tests passed locally, I will spend more time cleaning up new tests written for this PR.

[codecov]

Codecov Report

Merging #413 (2d1aa11) into main (ee23796) will decrease coverage by 0.08%.
The diff coverage is 96.25%.

@@            Coverage Diff             @@
##             main     #413      +/-   ##
==========================================
- Coverage   80.96%   80.88%   -0.09%     
==========================================
  Files         347      353       +6     
  Lines       22141    22554     +413     
==========================================
+ Hits        17927    18242     +315     
- Misses       4214     4312      +98     

Impacted Files	Coverage Δ
src/array/utf8/mutable.rs	89.91% <94.82%> (+1.29%)	⬆️
tests/it/array/utf8/mutable.rs	100.00% <100.00%> (ø)
src/compute/temporal.rs	83.78% <0.00%> (-10.07%)	⬇️
src/array/ord.rs	64.21% <0.00%> (-2.13%)	⬇️
tests/it/array/mod.rs	100.00% <0.00%> (ø)
tests/it/compute/temporal.rs	100.00% <0.00%> (ø)
src/compute/comparison/mod.rs	92.16% <0.00%> (ø)
src/compute/comparison/utf8.rs	67.41% <0.00%> (ø)
src/compute/comparison/binary.rs	67.41% <0.00%> (ø)
src/compute/comparison/boolean.rs	70.10% <0.00%> (ø)
... and 14 more

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[jorgecarleitao]

Awesome, looks great! 💯

Let two minor comments.

Feel free to move this to non-draft, change the title to be only for the MutableUtf8Array and we can merge this one.