feat: replace mulit statement parsing with comment aware parsing

[evadnoob]

existing multi-statement parsing was not aware of lines that start with -- this new function implementation could be extended in the future to support end of line comments as well as embedded comments.

for now I chose to go with a very naive scanner/lexer, it could easily be converted to use a state machine to emit statements, but this method is simple enough to be placed directly in migrate with little changes. Possibly good enough for now.