apacheGH-38630: [MATLAB] `arrow.array.BooleanArray`'s `toMATLAB` meth…

…od does not take slice offsets into account (apache#38636)

### Rationale for this change

While working on apache#38415, I noticed that the `toMATLAB` method of `arrow.array.BooleanArray` does not take the slice offset into account. This will cause the `toMATLAB` method to return the wrong value.

### What changes are included in this PR?

1. Updated `arrow::matlab::bit::unpack` function to accept a `start_offset` as input.
2. Updated clients (`BooleanArray::toMATLAB` and `Array::getValid`) to supply the array `offset` as the `start_offset`.

### Are these changes tested?

The existing tests cover these changes. Additionally, the changes for apache#38415 will include tests that verify the `toMATLAB` method returns the correct MATLAB array when the underlying Arrow array has been sliced.

### Are there any user-facing changes?

No.

* Closes: apache#38630

Authored-by: Sarah Gilmore <[email protected]>
Signed-off-by: Kevin Gurney <[email protected]>

apacheGH-38630: [MATLAB] `arrow.array.BooleanArray`'s `toMATLAB` meth…

…od does not take slice offsets into account (apache#38636)

### Rationale for this change

While working on apache#38415, I noticed that the `toMATLAB` method of `arrow.array.BooleanArray` does not take the slice offset into account. This will cause the `toMATLAB` method to return the wrong value.

### What changes are included in this PR?

1. Updated `arrow::matlab::bit::unpack` function to accept a `start_offset` as input.
2. Updated clients (`BooleanArray::toMATLAB` and `Array::getValid`) to supply the array `offset` as the `start_offset`.

### Are these changes tested?

The existing tests cover these changes. Additionally, the changes for apache#38415 will include tests that verify the `toMATLAB` method returns the correct MATLAB array when the underlying Arrow array has been sliced.

### Are there any user-facing changes?

No.

* Closes: apache#38630

Authored-by: Sarah Gilmore <[email protected]>
Signed-off-by: Kevin Gurney <[email protected]>

[maven-release-plugin] copy for tag apache-arrow-0.9.0

Apache Arrow JavaScript 0.3.1

Apache Arrow JavaScript 0.3.0

[maven-release-plugin] copy for tag apache-arrow-0.8.0

Apache Arrow JavaScript 0.2.0

[maven-release-plugin] copy for tag apache-arrow-0.7.1

[maven-release-plugin] copy for tag apache-arrow-0.7.0

[maven-release-plugin] copy for tag apache-arrow-0.6.0