Set up a sample iTwin repositories hierarchy

[grigasp]

For root nodes we'll want to use this query: https://developer.bentley.com/apis/iTwins/operations/get-repositories-by-itwin-id/.

Then, for each type of repository, we'll need to see what child nodes we could get (no strict requirements yet, just want to see that we can set up such a hierarchy).

• For "iModels" repository: https://developer.bentley.com/apis/imodels-v2/operations/get-itwin-imodels/
• For "RealityData" repository: https://developer.bentley.com/apis/reality-management/operations/get-all-reality-data/
• For "Storage" repository: https://developer.bentley.com/apis/storage/operations/get-top-level-folders-and-files-by-project/ and https://developer.bentley.com/apis/storage/operations/get-folders-and-files-in-folder/
• For "Forms" repository: https://developer.bentley.com/apis/forms/operations/get-project-form-data/
• ... and so on.

[grigasp]

Related: https://github.com/iTwin/3d-tiles-samples/blob/main/common/itwin/repositories.ts