Signal client resize in session packets

So far, scrcpy always resized the window whenever a frame with a new
size was received. However, with the upcoming "flex display" feature,
the size of the virtual display can change either on its own (e.g.,
due to app rotation) or as a result of a client window resize.

Track the cause of each resize and signal it in the session metadata.

Resize the window only if the change was not triggered by a client
request to prevent resize loops and stuttering.

PR #6772 <https://github.com/Genymobile/scrcpy/pull/6772>