Allow StringArray construction with Vec<Option<String>>

[sinistersnare]

Which issue does this PR close?

Closes #3599

Rationale for this change

This is an ergonomic addition, allows StringArrays to be constructed from more types (specifically Vec<Option> here.

What changes are included in this PR?

Added the impl, and fixed the tests that were ambiguous.

Are there any user-facing changes?

If a user tries to make a StringArray completely out of None values, before they could rely on it being inferred to a Vec<Option<&str>> impl. Now they must specify that (as shown in the test fixes).

This is possibly considered a breaking change.

Thanks!!

[sinistersnare]

I'm not sure how to add a tag, but if this should be considered a breaking change, the template said to add the appropriate breaking-change tag.

[viirya]

@tustvold already added "api-change" label.

[ursabot]

Benchmark runs are scheduled for baseline = 42b2d55 and contender = 3f72ebb. 3f72ebb is a master commit associated with this PR. Results will be available as each benchmark for each run completes.
Conbench compare runs links:
[Skipped ⚠️ Benchmarking of arrow-rs-commits is not supported on ec2-t3-xlarge-us-east-2] ec2-t3-xlarge-us-east-2
[Skipped ⚠️ Benchmarking of arrow-rs-commits is not supported on test-mac-arm] test-mac-arm
[Skipped ⚠️ Benchmarking of arrow-rs-commits is not supported on ursa-i9-9960x] ursa-i9-9960x
[Skipped ⚠️ Benchmarking of arrow-rs-commits is not supported on ursa-thinkcentre-m75q] ursa-thinkcentre-m75q
Buildkite builds:
Supported benchmarks:
ec2-t3-xlarge-us-east-2: Supported benchmark langs: Python, R. Runs only benchmarks with cloud = True
test-mac-arm: Supported benchmark langs: C++, Python, R
ursa-i9-9960x: Supported benchmark langs: Python, R, JavaScript
ursa-thinkcentre-m75q: Supported benchmark langs: C++, Java