Use a new directory path for creating directories

What does this MR do and why?

This MR aims to address Directories are always created in the root dire... (#344822 - closed) by using a subdirectory path if one exists when creating a new directory in the user interface.

Attribution: The code is heavily based on a proof-of-concept example provided by Hinam Mehra (@hmehra) in this slack thread. Thank you!

For context; the new directory modal was modified in 14.4, but there appears to be no validation of whether the new directory is made in a subdirectory, so everything is made at the project 'root' level.

Screenshots or screen recordings

Before	After
	TBD

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

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