DBSRV/GUI: Reduce time for select PV to appear and stop PV updating all the time

[John-Holt-Tessella]

As an instrument scientist, I would like the PV Selector dialogue to appear more quickly (it takes so long I think the GUI has died).
See #4922 as well which talks about reducing cpu load of the dbsrv.

Acceptance Criteria

1. PV selection dialogue appear in < 1s

Notes

I think the filter in the GUI is slow because it takes the list of all PVs and filters it by the list of interest X PVs and active. This is an nxm time filter which is quite big. I would suggest the all list has metadata added which is interest level and IOC. The list is then filtered by interest and IOCs that appear in IOCS PV. But please think about this yourself.
Code in the GUI is uk.ac.stfc.isis.ibex.ui.configserver.editing.pvs.PVSelectorPanel.setConfig the slow bits appear to be:
- blockPVTable.setRows(config.pvs());
- selectionChanged on source change
- selectionChanged on interest change
and possibly the refresh function in uk.ac.stfc.isis.ibex.ui.configserver.editing.pvs.PVSelectorPanel.addFilterListener

It maybe that the number of PVs can be reduced so that more information is put into a smaller number of PVs. The current pvs are (CS:BLOCKSSERVER:{}):
- PVS:ALL
- PVS:INTEREST:HIGH
- PVS:INTEREST:MEDIUM
- PVS:INTEREST:FACILITY
- PVS:ACTIVE
These should not update every second the code to do this is inst_server/DatabaseServer/database_server.py ln 191 (in DBSVR).

[John-Holt-Tessella]

Extra note the BDSVR seems to be the heaviest process taking 5% CPU on some machines.

[Tom-Willemsen]

Think about querying the database directly from the client.

[KathrynBaker]

It was considered early on, the main reason for making sure the information comes from the server as that does allow other clients other than IBEX GUI to look up that information

[Tom-Willemsen]

@John-Holt-Tessella split this ticket into 2