Refactor input validation code

[marta-]

• Separate functions for validating each component
• For health card validation: implement a map from province code to validation function plus a default validation function for .

[marta-]

Further improvements and fixes to current code:

• If all input lines are invalid, the button should remain disabled Won't do for now, as it may create confusion re why the button remains disabled
• When pasting content directly from a spreadsheet where the separator is \t, all lines are marked as invalid because of this separator
• For any line that contains a <health card, province> pair that was already encountered on a previous line, but with a different date of birth, invalidate and show the error:"ON health card number 1234567890 has already been entered on line 12 with a different date of birth" (where 12 is the line where the pair 1234567890,ON first appeared).