INTER: update slit panels on reflectometry OPI

[ThomasLohnert]

As an INTER scientist, I would like the reflectometry OPI to reflect the real state of the physical beamline. After the upgrade, they do not have a Slit4 anymore, so S4VG/HG should be removed. They would however like to control S3 in beam blocker mode, so a control for toggling this should be added (see POLREF screen in /reflectometry/POLREF/vgaps.opi in resources folder).

Acceptance Criteria

• Reflectometry front panel for INTER does not show S4
• Reflectometry front Panel for INTER does show S3 beam blocker toggle button
• Layout is clear and readable

Extra Information

Why it is needed?

Where required files/links are

How to Test

verbose instructions for reviewer to test changes
(Add before making a PR)

[ThomasLohnert]

PRs:
ISISComputingGroup/ibex_gui#1627
#8074

Scientists have since asked to add the activation parameter for Monitor 3 to the "important parameters" on the front panel so I have added that to this PR as well.