chore: Cleanup swf parsing

[madsmtm]

Refactor a few things in swf, no functional changes

[seanpm2001]

Thank you for helping to optimize this project. There is still a lot that needs to be fixed, but I don't know where to start, as I am not the best at Rust development. Shortening strings was a good step, and removing unneeded scripts was needed, however I don't know which ones caused the tests to fail. Code optimization is rare these days, and I appreciate when people take the time to do it. This definitely needs further review.
Also, don't be too hard on yourself. I wouldn't consider this to be a bad chore. I am hoping that you implied this to be a good chore, as it is.

[madsmtm]

Haha, yeah, definitely didn't mean this as a bad chore; I simply used that keyword to make it easy for others to see that this was a code-only change (in contrast to adding a feature or fixing a bug)

[Herschel]

Thanks, sorry for the delay!