imagebitmap: Remove ImageBitmap from experimental web platform features (#38050)

Enable by default the DOM "ImageBitmap" interface previously gated
behind
"dom.imagebitmap.enabled" preference as experimental web platform
feature.

https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#imagebitmap

NOTE: Non blocking non supported functionality:
- vector HTMImageElement, bitmap/vector SVGImageElement
- EXIF image orientation

Testing: Covered by existing WPT tests

Fixes: #34112

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

components/config/prefs.rs

@@ -84,7 +84,6 @@ pub struct Preferences {
     pub dom_fontface_enabled: bool,
     pub dom_fullscreen_test: bool,
     pub dom_gamepad_enabled: bool,
-    pub dom_imagebitmap_enabled: bool,
     pub dom_indexeddb_enabled: bool,
     pub dom_intersection_observer_enabled: bool,
     pub dom_microdata_testing_enabled: bool,
@@ -262,7 +261,6 @@ impl Preferences {
             dom_fontface_enabled: false,
             dom_fullscreen_test: false,
             dom_gamepad_enabled: true,
-            dom_imagebitmap_enabled: false,
             dom_indexeddb_enabled: false,
             dom_intersection_observer_enabled: false,
             dom_microdata_testing_enabled: false,