[FEATURE] upgrade `fileLocations` to support Create+Update+Delete

[JoernBerkefeld]

There was a new API endpoint introduced for this type in Spring 22, described here: https://developer.salesforce.com/docs/marketing/marketing-cloud/guide/fileTransferLocationManagement.html

Supported Use Case	HTTP Verb	URI
Create a file location	POST	data/v1/filetransferlocation
Get the file locations	GET	data/v1/filetransferlocations
Get a single file location	GET	data/v1/filtransferlocation/{customerKey}
Update a specific file location	PATCH	data/v1/filtransferlocation/{customerKey}
Deactivate a specific file location	DELETE	data/v1/filtransferlocation/{customerKey}

Warning: Potentially, this new endpoint only covers EXTERNAL fileLocations. Needs to be confirmed before replacing the existing logic.