add readback, updates, and status PVs

This merge addresses following issues:

• Fan speed PV was missing update, so it stayed 0/invalid whole time
• Add readback records to all input fields used in nice/guis/gui-drvasyniseghalservice!1 (merged)
• Add 2 status monitoring PVs, to be used in nice/guis/gui-drvasyniseghalservice!1 (merged)

Related links:

• Jira: https://jira.ess.eu/browse/ICSHWI-20872 https://jira.ess.eu/browse/ICSHWI-21234
• Confluence: https://confluence.ess.eu/display/IS/RF+Bias+PS+HV+System
• IOC: https://gitlab.esss.lu.se/iocs/manual/dream/e3-iocs-dream-dtcmn-sc-ioc-008
• Epics module: !3 (merged)
• OPI: nice/guis/gui-drvasyniseghalservice!1 (merged)
• Conda: e3/recipes/drvasyniseghalservice-recipe!2 (merged)