Add .ui file to MVP file generator

[adriazalvarez]

Description of work

This PR slightly modifies the way to generate the GUI used in the MVP generation tool #37813 to work with .ui files, which is a more common way to operate with GUIs in Mantid.

Summary of work

This PR adds a .ui file that generates a simple qt widget (same as the one generated programatically in #37813).
Additionally, I have modified the corresponding view files and cmake files as well as the template.py generator function to account for the inclusion of the .ui file

Fixes #37977

Further detail of work

To test:

• Test that the MVP generation tool works correctly following the python and cpp examples: https://developer.mantidproject.org/MVPDesign.html#mvp-template-tool

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