Library_Engine: Add protection when trying to read massive custom folders

#### Description:

After the support of https://github.com/BHoM/BHoM_Engine/pull/2648 it is possible to get the Library_Engine to extract from more places than the standard C:\ProgramData\BHoM\Datasets .

If someone, by accident, adds a root folder, like the C:\Users\_USERNAME_ folder here, it means the Library_ENgine will try to run through every single folder and file in there and try to extract every json file it finds as a library.

Some protection is in place, that does not allow you to add the whole C drive, but more might be needed to make sure things do not crash, especially is Settings is presistent across a fresh install of the BHoM (intentionally), which means that standard solution is not feasible.

#### Expected behaviour:

For as little restriction as possible to be put on what you can and can not add as user folders, but make sure the whole system does not crash if someone by accident or not, has put a folder like the whole User folder as a library path.

#### Test file(s):