Expose Testing Utils for Mocking FS in Unit Tests that hit paths that involve Inference Plugins

[Coly010]

The issue occurs because the unit test process itself is running within the context of an Nx Workspace which has an Inference plugin set up.
This interferes with the unit testing process when the generators under test perform actions that require loading the crystal plugin.

The solution is to ensure the unit tests are run in a separate directory than the Nx workspace.

Within Nx itself, we use a util called TempFS that we have not yet exposed to circumvent this issue.

The original issue was posted here: #30177

We should expose the TempFs or a similar utility to plugin authors.