feat(gst): enhance GStreamer integration with new modules and improved API

This commit introduces significant enhancements to the GStreamer integration by:
- Adding new modules for bins, caps, elements, pads, and plugins
- Implementing a more ergonomic API with helper methods like play(), pause(), ready()
- Adding support for various GStreamer plugins including app, autodetect, playback, and videoconvertscale
- Improving error handling with better context attachment
- Updating dependencies to latest versions including gstreamer-video 0.24.4
- Refactoring existing code to use modern Rust patterns and features

gst/src/element.rs

@@ -0,0 +1,52 @@
+use crate::{Error, Pad, Result, ResultExt};
+#[repr(transparent)]
+pub struct Element {
+    pub(crate) inner: gstreamer::Element,
+}
+
+pub trait IsElement {
+    fn as_element(&self) -> ∈
+    fn into_element(self) -> Element;
+    fn pad(&self, name: &str) -> Option<Pad> {
+        use gstreamer::prelude::*;
+        self.as_element().inner.static_pad(name).map(Pad::from)
+    }
+}
+
+impl IsElement for Element {
+    fn as_element(&self) -> &Element {
+        self
+    }
+
+    fn into_element(self) -> Element {
+        self
+    }
+}
+
+pub trait Sink: IsElement {
+    fn sink_pad(&self) -> Pad {
+        use gstreamer::prelude::*;
+        self.as_element()
+            .pad("sink")
+            .map(From::from)
+            .expect("Sink element has no sink pad")
+    }
+}
+pub trait Source: IsElement {
+    fn source_pad(&self) -> Pad {
+        use gstreamer::prelude::*;
+        self.as_element()
+            .pad("src")
+            .map(From::from)
+            .expect("Source element has no src pad")
+    }
+
+    fn link<S: Sink>(&self, sink: &S) -> Result<()> {
+        use gstreamer::prelude::*;
+        self.as_element()
+            .inner
+            .link(&sink.as_element().inner)
+            .change_context(Error)
+            .attach("Failed to link source to sink")
+    }
+}