Support passing in migrations directly rather than glob files on disk

[tonyxiao]

We are using slonik migrator as part of an api call on next.js, and it is really tricky to package up the sql files while maintaining the directory hierarchy. It would be so much easier if we can simply pass the migrations into slonik migrator while instantiating in typescript

[mmkal]

I agree - this is a feature of https://github.com/sequelize/umzug which I also maintain. @slonik/migrator adds some high-level convenience stuff specific to postgres and slonik on top of that. But I would like to eventually bring all the latest niceties from umzug over here too. I'm slightly blocked on doing updates generally while I wait on some changes to slonik itself though. In the meantime, worth looking into umzug if you want direct/low-level control.