misc: update minify trace logic to date

[patrickhulce]

Summary
Our trace minification logic got out of sync with some of our lantern improvements of the past few months. This PR fixes that, refactors it to a lib, and adds some tests while we're at it so it won't get out of sync again.

Related Issues/PRs
closes #8949

[brendankenny]

sorry to be lazy, but could you add some comments about which files moved where vs what's new? :D:D

[brendankenny]

jk, that might be too lazy. This is two moved files and two new test files :)

[brendankenny]

LGTM, just some small things and questions

There's probably an argument for moving them into some sub directory in lib/, but also seems fine enough there :)

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