fix: Make extent/size of floating windows clearer

[briandipalma]

No description provided.

[briandipalma]

This is what it looks like with my change:

border: "none"

border: "single"

border: "double"

border: "rounded"

border: "solid"

border: "shadow"

Custom border - the way I think Neovim should be by default for the single/double/rounded borders above

telescope

I'll post screenshots without my change next.

[briandipalma]

This is what it looks like without the change:

border: "none" - no change

border: "single" - improvement as you can now see correct size of floating window

border: "double" - improvement as you can now see correct size of floating window

border: "rounded" - improvement as you can now see correct size of floating window

border: "solid" - improvement as you can now see correct size of floating window, really bad looking without the change

border: "shadow" - no change

Custom border - improvement, clearer definition of floating window

telescope - no change

[mvllow]

Appreciate all the before/after screenshots as well as you changing the PR to work with the latest update :)