(feat) O3-5210: Make queue priority optional

[makombe]

https://openmrs.atlassian.net/browse/O3-5210

[chibongho]

Instead of making queue priority optional, would it be ok to just create a placeholder priority type for patients who have not yet been triaged?

[ibacher]

The priority is required because a priority queue without a priority doesn't make any sense. If we need a priority for non-triaged patients, just create a "Non-Triaged" priority or something similar.