ON HOLD: add no-floating-promises eslint rule

[shouples]

Important

This PR will be periodically updated with main after we've had a chance to clean up some of the offending areas of the codebase so we don't try and merge a huge changeset in from this branch. Once gulp lint is green in this branch, the only changes going in should be from eslint.config.mjs.

This rule will flag any calls returning a Promise that aren't awaited.

https://typescript-eslint.io/rules/no-floating-promises/

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This currently shows a lot of failures (100+) during gulp lint:

...but we can create some PRs based on this branch to slowly chip away at the different offenders either through adding the void operator, awaiting the promise, or adding the following above an offending line:

// eslint-disable-next-line @typescript-eslint/no-floating-promises

[shouples]

Closing since it's set to warn on main, so we can chip away at the remaining <50 warnings when time permits.