DYN-7082: Improvements to node List.IndexOf

[reddyashish]

Purpose

https://jira.autodesk.com/browse/DYN-7082
In reference to #15268, to avoid negative index values being returned, we modified IndexOf that will return null when the element is not found in the list.

Before:

After:

Declarations

Check these if you believe they are true

• The codebase is in a better state after this PR
• Is documented according to the standards
• The level of testing this PR includes is appropriate
• User facing strings, if any, are extracted into *.resx files
• All tests pass using the self-service CI.
• Snapshot of UI changes, if any.
• Changes to the API follow Semantic Versioning and are documented in the API Changes document.
• This PR modifies some build requirements and the readme is updated
• This PR contains no files larger than 50 MB

Release Notes

DYN-7082: Improvements to node List.IndexOf

Reviewers

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[github-actions]

See the ticket for this pull request: https://jira.autodesk.com/browse/DYN-7082

[github-actions]

UI Smoke Tests

Test: success. 11 passed, 0 failed.
TestComplete Test Result
Workflow Run: UI Smoke Tests
Check: UI Smoke Tests

[mjkkirschner]

why does this return a string?

[reddyashish]

Because we want to return null(and not -1) if the element is not found in the list. After this change, #15205, passing -1 as index would get the last element from the list.

[mjkkirschner]

yeah I'm not getting it -
Because we want to return null(and not -1) - so just return null from a regular index function that returns int|null - what does this function returning a string|null index help?

[reddyashish]

Got it, my bad for misunderstanding. Changes should be fine now.

[QilongTang]

@reddyashish Maybe add screenshot for behavior diff?

[QilongTang]

Updated PR description