Merge editor.largeFileSize and editor.largeFileLineCount

[alexdima]

As @isidorn points out in #44986 (comment), most likely people will want to turn off the limitations, and giving a value is more or less meaningless...

We could have a single setting called editor.largeFileOptimizations and turn it to false. @isidorn any better ideas for the setting name ?

[isidorn]

I like that setting name, I would in the hover describe the idea and warn the user that changing the default behavior could lead to vscode being unresponsive when opneing large files.

The only issue with that name is that I would not be 100% sure what does true and what does false mean. Is optimisation to allow to fastly open it (default) or to show highlights
I understand as a developer that it is the first, but for hte user might not be so clear.
So I would try to address this in the hover. That optimizations means speedup

[alexdima]

There is now a single setting called editor.largeFileOptimizations with the following description: "Special handling for large files to disable certain memory intensive features".