Replaced our custom MultiLookup with the Codex MultiSelectLookup component

According to the related tickets:

• Replaced our custom MultiLookup with the Codex MultiSelecctLookup component for Contextual Attributes, Location and Compliance Requirements components
• Contextual Attributes field is now included as a part of the Schema details section

Also a few minor fixes:

• Some issues related to the "What would you like to do" section at the top of the form (the page was blank when user chose a different action using the radio buttons)
• When modifiying an instrument, there was an error when leaving contextual attributes field empty
• The width of the message for the Catalog View has been fixed (it was shorter than expected due to some previous restyling work)
• Sampling.vue is now considered as a form component (so far it was added via `Specifications.vue` and that was a bit confusing

Closes T369912, T377823