Add a cli option to start as 1:1

I’m not sure I fully understood why scrcpy does not start as 1:1 right away on my computer since the window does fit on screen after I press ctrl+g.

But there should be a cli option to start as 1:1 anyway as it can be useful is some situations, even when it does not fit on screen.

Start by locating scrcpy's command-line option parsing and the code handling the Ctrl+G 1:1 resize behavior. Trace how the initial window size is selected, then verify that a new option starts at 1:1 even when the window does not fit on screen.

Written by the indexing model from the issue text.