FIX: CP link instead of CPP link

[klauer]

Context

Closes #282

Prior to this PR, we are erroneously limited to 2Hz updates for all IOC->PLC PV links due to the 0.5 second SCAN rate configured for linked records. What we want is the IOC to write to the PLC on every update, and failing that at 2Hz.

Background

• A CPP link means "channel access link which causes processing (when the monitor is fired), only if the record's scan field is set to Process Passive
• A CP link means "channel access link which causes processing (when the monitor is fired), regardless of the record's SCAN field

In our case, we want the linked record to cause processing on every update. This is how the mechanism is supposed to work with pytmc writing values from the IOC to the PLC.

[ZLLentz]

Code change + test fixes looks good- merge at will if it was passing locally Should follow-up later to fix the CI troubles