Move first request_animation_frame into resize observer

[jprochazk]

This PR ensures the first animation frame happens after the resize observer has had a chance to do its job.

• Closes Web canvas size is tiny for the first frame #4622

The first commit contains some log calls to observe the changed behavior:

Before:

[eframe::web::app_runner] eframe/src/web/app_runner.rs:191: LOGIC [300.0 150.0]
[eframe::web::events] eframe/src/web/events.rs:633: ResizeObserver canvas=[300.0 150.0] to=(1920, 993)
[eframe::web::app_runner] eframe/src/web/app_runner.rs:191: LOGIC [1920.0 993.0]
[eframe::web::app_runner] eframe/src/web/app_runner.rs:191: LOGIC [1920.0 993.0]

After:

[eframe::web::events] eframe/src/web/events.rs:633: ResizeObserver canvas=[300.0 150.0] to=(1920, 993)
[eframe::web::app_runner] eframe/src/web/app_runner.rs:191: LOGIC [1920.0 993.0]
[eframe::web::app_runner] eframe/src/web/app_runner.rs:191: LOGIC [1920.0 993.0]

[emilk]

nice