non-awaited async calls

[danielpeintner]

You may have noticed the build is failing on a flaky tests.
I found the issue coming from a non-awaited async call.

Therefore I have activated the "@typescript-eslint/no-floating-promises": "warn", as rules.

This rule allow me to easily find the issue.

(we have 100 places where un-awaited promised functions call are missing catches, I only fixed in binding-opcua ) for the time being.

Originally posted by @erossignon in #1424 (comment)

[danielpeintner]

See fixes for OPCUA in #1424.

[danielpeintner]

relates to #1446