ON HOLD: add no-floating-promises eslint rule

[shouples]

Summary of Changes

Top level PR for any calls returning a Promise that aren't awaited.

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

Pull request checklist

Please check if your PR fulfills the following (if applicable):

Tests

• Added new
• Updated existing
• Deleted existing

Other

• All new disposables (event listeners, views, channels, etc.) collected as for eventual cleanup?

• Does anything in this PR need to be mentioned in the user-facing CHANGELOG or README?
• Have you validated this change locally by packaging and installing the extension .vsix file?

  gulp clicktest