Breaking change in FileSystemTreeControllerBase #20602
Description
Which Umbraco version are you using?
16.3.0
Bug summary
Umbraco forms uses FileSystemTreeControllerBase to list razor files to select as an email template. It does this by overriding the FileSystem property to set the location where razor views should live. In 16.3.0 however the FileSystem property has been obsoleted but it's functionality has been replaced with an IFileSystemProvider lookup from the DI container, which for some reason is defaulting to the scripts file system provider.
Specifics
No response
Steps to reproduce
See replication steps in this Forms issue umbraco/Umbraco.Forms.Issues#1472 (comment)
Expected result / actual result
I would expect that the obsolete FileSystem property would continue to work and be the source of the filesystem operations and only if it isn't present should it fallback to new behaviour.