Apply filter on selected spectra

[lpatiny]

@jwist is interested to be able to phase correct many spectra at once.

[hamed-musallam]

@lpatiny

This is something we need to discuss. The current behavior assumes only one spectrum is selected. If we plan to change this, we need to carefully consider how the processing panel will handle multiple spectra being selected and ensure that the tool remains visible. This primarily affects the UI, but there are also underlying aspects that will need refactoring.

Additionally, I think this change shouldn't be limited to phase correction, it should be applied to other filters as well

[lpatiny]

Yes this is something we should discuss but it is not urgent.