Remove `sleep` in favor of async/await

[christian-bromann]

Describe the bug Putting the process to an halt with:

    const stop = new Date().getTime() + ms;
    while(new Date().getTime() < stop);

is not ideal as it completely blocks everything from happening. We should replace this and all functions with proper async/await logic. I see similar implementations in all do { ... } while (...) places.

Log n/a

To Reproduce n/a

Expected behavior Use async/await instead of this.

Environment (please complete the following information):

• wdio-video-reporter version: [e.g. 1.1.2]
• WebdriverIO version: [e.g. 5.4.13]
• Mode: [Standalone mode or WDIO Testrunner]
• If WDIO Testrunner, running sync/async: [e.g. sync/async]
• Node.js version: [e.g. 8.11.2]
• NPM version: [e.g. 5.8.0]
• Browser name and version: [e.g. Chrome 68]
• Platform name and version: [e.g. Windows 10]

Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context Add any other context about the problem here.