Improve global scope situation with util and lint update

[peaBerberian]

Some years back, we were notified of an issue when the RxPlayer was imported in a Node.JS environment - which has mostly no chance to bring any result unless that environment implements MSE, EME and DOM API - but which was still done due to some application logic linked to server-side-rendering.

That issue lead to an error, and was due to the RxPlayer refering to the window (the global scope accessible in JavaScript in a main thread environment) at the top level (generally done there to check once at script evaluation if various browser API are present), because window does not exist in Node.JS environments.

What we did at the time is just to check (poorly) if we were in a Node.js environment, and to not rely on window if that was the case at those various places. However that was error-prone (we could forget that check) and the only thing preventing mistakes was a script in scripts/check_nodejs_import_compatibility.js which wouldn't be able to catch all cases.

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Because this became again a problem when PoCing worker environments, I profited from this project to work on a better solution.

Now the global scope is directly provided by an util function of our compat code, which works for NodeJS, JS main thread and JS WebWorker environments, and its usage is enforced by a linter rule which should hopefully catch most window usage in the code.

I also chose to erase all usage of the term window or the shortened win alias in code to better communicate the point that we're specifically mean the global scope, regardless of how it is referred to in the current environment.