👔 Handle user-defined motion estimate filters

[shnizzedy]

Related problem

This change will require an update to the GUI to generate filters similar to how regressors and handled specially.

― FCP-INDI/C-PAC#1837 (comment)

Proposed feature

Add a specific component like Regressor for handling motion estimate filters

Acceptance criteria

• GUI can create an arbitrary number of valid motion estimate filters in a pipeline

Alternatives

GUI creates an empty list for motion estimate filters and directs the user to User Documentation » Setting Up A Pipeline Configuration » Pre- and post-processing » Functional Preprocessing: Initial Preprocessing § Configuration Without the GUI

Additional context

If / when we convert the validation schema to JSON Schema, we should revisit the design of these "USER-DEFINED" components (Regreossor and MotionEstimateFilter) to SSOT them, with the source of truth being the validation schema