Make project level cli work inside subdirectory (#531)

Description

Fix a bug which prevents importng the CLi with kedro==0.19.4 because I relied on private _is_project.
On the way, make all project level CLI (init, ui, and modelify) work inside a subdirectory and not only at the root of kedro level

Create my own _is_project and _find_kedro_project functions which manges the import of the private functions of kedro.
Change all CLI to get the project path with _find_kedro_project instead of taking Path.cwd.

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