ReadASCII: lookup table settings lost on IOC restart

As a user of any IOC which uses ReadASCII's PID lookup table, I would like the settings I have selected to either persist through IOC restarts, or be settable via configuration macros.

Currently we can't use a typical initialisation routine (e.g. setting `VAL` and `PINI="YES"`) because ReadASCII does some internal initialisation and overwrites those values. We should fix (and document!) how to correctly initialise:
- Lookup table name
- Whether the lookup table is in use or not

As part of https://github.com/ISISComputingGroup/IBEX/issues/4103 a workaround is implemented in the Triton driver based on a `seq` record waiting 10 seconds before sending the initial values, but this is not a good long-term solution. Remove this workaround in the Triton driver once this ticket is complete.