feat: Introduce SampledProperty new function getSample

[s3xysteak]

Description

The PR add a new function getSample to SampledProperty, which provides a feature to get the time of samples by index.

Issue number and link

Closes #12245.

Testing plan

Technically speaking, it only performs simple operations on arrays. I add a simple unit test to check if it works well.

Author checklist

• I have submitted a Contributor License Agreement
• I have added my name to CONTRIBUTORS.md
• I have updated CHANGES.md with a short summary of my change
• I have added or updated unit tests to ensure consistent code coverage
• I have updated the inline documentation, and included code examples where relevant
• I have performed a self-review of my code

[github-actions]

Thank you for the pull request, @s3xysteak!

✅ We can confirm we have a CLA on file for you.

[ggetz]

Thanks for the PR @s3xysteak!

@lukemckinstry Could you please review?

[lukemckinstry]

Thanks @s3xysteak for this PR!
Looks good 👍 One minor question.
@ggetz you may want to take a quick look as well.

[lukemckinstry]

Do you think it would be good to check that the index is within range? Or is it better to allow an out of range index and return undefined?

if (index < -this._times.length || index >= this._times.length) {
throw new DeveloperError("Index out of bounds.");
}