Add missing RenderingDevice method descriptions

[ARez2]

I went through the RenderingDevice.xml file and added all the missing descriptions of methods. I also updated some descriptions to be more complete.

This is in an effort to become more familiar with the Godot source code, specifically compute shaders.

[AThousandShips]

Thank you for your contribution! Some phrasing and grammar details

[ARez2]

Thanks for the quick review @AThousandShips . I fixed those issues and committed your suggestions. I also squashed the suggestion commit back into one commit :D

[AThousandShips]

Great! I'm not exactly sure of the exact wordings and someone else will come around as well to review it, just added some suggestions on things where I thought it'd help

[ARez2]

Yes those were some good suggestions. Especially the "ranging" stuff ^^ Also my bad for having a typo in the first place. I forgot to set up my pre commit hooks properly.

[RedMser]

Suggested some things I randomly noticed

[ARez2]

Alright added all your suggestions too @RedMser . Thanks for looking over it ^^

[ARez2]

Alright, once again merged everything together. I also removed the double space after "clearing" (as mentioned by @akien-mga )

[clayjohn]

Looks great! Good work

[Calinou]

I'd prefer "Prints an error" as opposed to "Throws an error", as Godot doesn't use exceptions.

[akien-mga]

Looks good! Could you squash the commits? See PR workflow for instructions.

[ARez2]

Alright! I think I got everything right now. When trying to commit the changes @Calinou suggested, I must have messed something up and had a bunch of other commits in my branch history.
It also had created a "Merge branch 'master' of https://github.com/ARez2/godot into add-rd-method-descriptions" which I am not sure why it did. So I was not sure what exactly to do in the rebase. I did multiple git rebase -i upstream/master before, but this time in the editor window that openend, there weren't 2 commits, but only that one "Add missing RenderingDevice method descriptions" commit. So I just picked that one and that seemed to have rerolled the branch commit history to the correct state.

TLDR: My faults are fixed now and everything should be correct now.

[akien-mga]

Thanks!

[YuriSizov]

Cherry-picked for 4.1.3.