tatt: future prospects

[arthurzam]

Many ideas from https://github.com/pkgcore/pkgdev/issues/149#issuecomment-1844919325

### Stage 1
- [x] https://github.com/pkgcore/pkgdev/issues/149
- [ ] Have the ability to never select certain flags
- [ ] Have the ability to force select certain flags
- [x] Have a specific *package.env* file to source
- [ ] Limit runs when used all options