Detect floating promises with ESLint

[t1m0thyj]

As a Zowe Explorer developer,
I want to eliminate floating promises from our code base,
to prevent uncaught promised exceptions which are difficult to debug.

[t1m0thyj]

Discussed with @traeok and originally we deliberately disabled the @typescript-eslint/no-floating-promises for our codebase because it caused a number of false positives around Thenables used by VS Code API methods like vscode.window.showInformationMessage.

Perhaps we could add a customized version of the no-floating-promises rule to our ESLint plugin that enforces the rule only for promises that implement a .catch method.