PV values: add local toggle

We should add a local tickbox, like we do for blocks, on PV sets/values on a config/component. Currently i think they default to absolute PVs.
This would make #7515 a whole lot easier as we wouldn't need to work out if a pv set is local or not.

### Acceptance criteria
- A user can select local/non-local when adding a pv set to a config
- An upgrade step is added to retroactively add this to any existing PV sets and default them to non-local

Start by tracing where PV sets are added to a config or component, then compare that flow with the existing local tickbox for blocks. Find the project's upgrade mechanism and verify how existing PV sets are migrated. Done means users can choose local or non-local when adding a PV set and existing sets are explicitly defaulted to non-local.

Vom Indexierungsmodell aus dem Issue-Text verfasst.