Deprecate PrintTranscriptDialog and just use PrintDialog

[rocodes]

Description

When working torwards #1777 I included some refactoring that would make it easier to stop using separate dialogs for each Export action, and the refactor happened on the usb export side (so exporting a transcript and exporting one or more files now all used the same ui element, in that case, a wizard). The method signatures for the PrintTranscriptDialog and PrintDialog have already been refactored to prepare for this, so let's deprecate PrintTranscriptDialog and just use one PrintDialog throughout.

This is also a good time to change the method signature of _on_print_preflight_check_failed and _on_print_failed in print_dialog.py to just return an ExportStatus, instead of ExportError(ExportStatus) (and to change the corresponding print_preflight_failed and print_failed signals in export.py to match. That lines us up for further imrpovements/simplifications down the line: ultimately we should deprecate the Modal Dialog style anyway (when we overhaul printing), but for now, this will allow us to DRY things up and make other improvements such as #918 more easily.

How will this impact SecureDrop users?

No immediate user-facing changes, but maintaining fewer UI elements will lead to more consistency and fewer bugs.

How would this affect the SecureDrop Workstation threat model?

N/a

User Stories

As a user, I want a consistent experience across all similar actions (Exporting, printing)
Developer QoL: As a developer, I want to avoid maintaining duplicative code