DETMON: Enable read-only IOC monitoring

[JamesKingWork]

As someone supporting IBEX and the detector monitoring systems at ISIS, I want to monitor a number of HVCAENs in read-only mode from DETMON.

A read-only option for the HVCAEN IOC was implemented in #4184 and is part of the latest release.

Davide Raspino will provide a number of IP addresses for the HVCAENs to monitor.

Acceptance criteria:

• Latest release is deployed to DETMON containing the read-only HVCAEN IOC option This has already been done in Deploy: DETMON #5596
• HVCAEN IOC is loaded in read-only mode and points to the provided IP Addresses
• There are blocks on the Name, V0Set, I0Set, VMon, IMon and Status variables of each channel we are monitoring
• Channel data logged as blocks
• Modify the blockserver to add the ability to specify a gwblock.pvlist and block_config.xml file in a configuration to configure the block gateway and archiver in a customisable way

Notes:

• See current DETMON config for when to log changes in channel values

[John-Holt-Tessella]

Impeded because CAEN will probably be turned off

[JamesKingWork]

There are currently no blocks set up on DETMON because the CAEN crates are not giving any data. I have confirmed that this is nothing to do with the read only mode. I will set up blocks when the CAEN crates are back on. Details of how to do this are here https://github.com/ISISComputingGroup/IBEX/wiki/DETMON-Instrument-Details#configuration-set-up