Remove splitting by spaces from process/command helpers (#7093)
* Remove splitting by spaces from process/command helpers
Accepting strings and splitting by spaces is unsafe if paths or arguments could contain spaces. Accepting strings makes it really easy to make this mistake.
I propose we stop taking strings in this way and if we want to use strings for convenience we force calling `.split(' ')` at the call site (on the literal string). This makes it easier to spot these kinds of bugs... if you are calling `.split(' ')` on a string that contains a variable, you might have a bug. It's safe to call it on a simple literal string where you can easily see that it can't split incorrectly.
* Always use List<String> for args