AUv2: take a request_resize made inside gui->create() as the view's initial size

[busticated]

Fixes #582.

initWithAUv2: runs gui->create() before [super initWithFrame:], so a request_resize() from inside create() calls setFrame: on an uninitialized view causing AppKit to throw. With the changes here, while create() runs, setFrame: stores the requested size and initWithAUv2: uses it as the initial frame.

Tested with pluginval's (v1.0.4) AU editor test on a nice-plug-egui plugin - it aborts on v0.16.0 without this change and passes with it.

All CI jobs pass on next - see here: https://github.com/busticated/clap-wrapper/actions

Happy to address any feedback - hope it helps 🙏 👍

[busticated]

closing in favor of #594, which fixes #582 more elegantly by initializing the view before create(). verified against our repro; details on #594.