Functions for filesystem operations

[SteveL-MSFT]

Summary of the new feature / enhancement

Looks like Bicep has added a bunch of new functions to work with the filesystem which would be useful for DSC. Azure/bicep#2501

Proposed technical implementation details (optional)

No response

[SteveL-MSFT]

@Gijsreyn do you want to take this one?

[Gijsreyn]

@SteveL-MSFT - I just hit up a PR around loadTextContent() and loadFileAsBase64(). Do you also want the remaining two, e.g., loadYamlContent() and loadJsonContent()? See: https://learn.microsoft.com/en-us/azure/azure-resource-manager/bicep/bicep-functions-files

[SteveL-MSFT]

@Gijsreyn yeah, we should probably include those, but can be separate PR

[Gijsreyn]

Already thought so. I'll hit up a separate PR for that!