chore: Remove various IE hacks and workarounds

[gonfunko]

The basics

• I branched from develop
• My pull request is against develop
• My code follows the style guide
• I ran npm run format and npm run lint

The details

Resolves

#6325, aside from base.js.

Proposed Changes

Removes various IE-specific hacks from the codebase.

Test Coverage

Ensured tests pass, and tried to poke at the affected codepaths in Chrome. It'd probably be good to verify these changes in (modern) Edge, but I don't have any machine that runs it.

[BeksOmega]

LGTM! But sadly I also do not have access to a machine that can run edge :/

[rachel-fenichel]

You can use browserstack.

[rachel-fenichel]

And if you don't want to use browserstack, you can push it up to a site that I can access from my personal laptop and I can follow instructions to test it. I am not set up to build blockly locally on that laptop though, and don't want to be :)

[BeksOmega]

I tested on browser stack, and Rachel tested locally! looks good =)