Disallow editing "Decision after consultation" in edit consultation form

[rithviknishad]

Describe the bug
Suppose a consultation is filed with "Admission" and so the admission date is captured and when we edit a consultation, we are currently allowed to change the decision after consultation. Suppose we change it to Out-Patient (where we wouldn't record an admission date), we now have a consultation record with Out-patient as suggestion and also has an admission date.

To Reproduce
Steps to reproduce the behavior:

1. Do what was said above

Suggested behavior(s)

• We shouldn't allow changing decision after consultation
• We should sanitize and remove the admission date if captured (but changing back to "Admission" due to accidental edit would mean we lost the initially captured admission date
• Ignore and leave it to the one who extracts data from the records to decide on whether to focus on conditional fields or not

[rithviknishad]

Continued in #6668 #6669