[IDEA] Resolve inconsistencies between cascade filter run prefix and file system path filters

[saqimtiaz]

The implementations of the cascade filter run prefix and the mechanism used to apply the $:/config/FileSystemPaths filters are very similar but different. This can lead to confusion for end users over which variables are available and how the filters are evaluated. We should investigate whether we can evaluate $:/config/FileSystemPaths as a cascade filter run, or re-using the code from the filter run prefix, without breaking backwards compatibility.

The differences include whether the title passed to the cascade is available in the variable currentTiddler and also the availability of global variables. See #8561 and #8520

If this proves not to be possible, we should explore making the two implementations are similar as possible, for example by setting the variable currentTiddler to the title of the tiddler being evaluated in $:/config/FileSystemPaths