Lint to prevent floating promises (#2497)

Fixes #1984

Note that I just mechanically went through all the errors and tried to
fix them. We definitely need to look at the change log and decide if we
like the changes. Maybe we should add a few more if statements with
throw instead of asserting not now and so on.

## Checklist

- [/] I have added
[tests](https://www.cursorless.org/docs/contributing/test-case-recorder/)
- [/] I have updated the
[docs](https://github.com/cursorless-dev/cursorless/tree/main/docs) and
[cheatsheet](https://github.com/cursorless-dev/cursorless/tree/main/cursorless-talon/src/cheatsheet)
- [/] I have not broken the cheatsheet

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Co-authored-by: pre-commit-ci-lite[bot] <117423508+pre-commit-ci-lite[bot]@users.noreply.github.com>
Co-authored-by: Pokey Rule <[email protected]>

Author: 3 people