Dispensing: Prescribed Quantity improvements

[jmbrunskill]

Record only 1 prescribed quantity

Due to a bug in mSupply (https://github.com/msupply-foundation/msupply/issues/16070) prescribed quantity can double in mSupply when applied to multiple lines.
Open-mSupply should align with the updated mSupply, storing the prescribed quantity on just one line

Allow recording prescribed quantity on a placeholder line

At the moment if there's not stock available, it's not possible to record a prescribed quantity against that item.
In this scenario, we should allow the user to record the prescribed quantity against a placeholder line (e.g. an invoice line that's not associated with a stock line)

Acceptance Criteria 🧾

• Prescribed Quantity should only be saved on the first allocated line in the prescription.
• Only 1 line should have prescribed quantity per prescription per item.
• If the line containing the prescribed quantity is deleted or allocated 0 stock, the prescribed quantity should be saved to the next line.
• Prescribed quantity can be saved against a placeholder line if no stock is allocated for that item

Epic Link 🔗

#6000

Moneyworks Jobcode 🧰

OMS:CIDV

[GeronimoJohn]

Improvements have been merged to #6180