imagebitmap: Use snapshot::Snapshot as bitmap data (#37131)

Replace the holder of actual pixel data of the ImageBitmap interface
([[BitmapData]] slot) from Vec<u8> to snapshot::Snapshot (image bitmap
with metadata).
https://html.spec.whatwg.org/multipage/#the-imagebitmap-interface

It will allow to have all required information (e.g. size, pixel format,
alpha mode)
for further drawing processing to/from canvas2D output bitmap.

Testing: No required tests
Fixes: https://github.com/servo/servo/issues/34112

Signed-off-by: Andrei Volykhin <andrei.volykhin@gmail.com>

components/shared/constellation/Cargo.toml

@@ -31,6 +31,7 @@ net_traits = { workspace = true }
 profile_traits = { workspace = true }
 serde = { workspace = true }
 servo_url = { path = "../../url" }
+snapshot = { workspace = true }
 strum = { workspace = true }
 strum_macros = { workspace = true }
 uuid = { workspace = true }