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/pad.rs

@@ -0,0 +1,31 @@
+use crate::*;
+/// Pads are link points between elements
+#[repr(transparent)]
+pub struct Pad {
+    pub(crate) inner: gstreamer::Pad,
+}
+
+impl From<gstreamer::Pad> for Pad {
+    fn from(inner: gstreamer::Pad) -> Self {
+        Pad { inner }
+    }
+}
+
+impl Pad {
+    pub fn ghost(target: &Pad) -> Result<Pad> {
+        let ghost_pad = gstreamer::GhostPad::with_target(&target.inner)
+            .change_context(Error)
+            .attach("Failed to create ghost pad")?;
+        Ok(Pad {
+            inner: ghost_pad.upcast(),
+        })
+    }
+    pub fn activate(&self, activate: bool) -> Result<()> {
+        use gstreamer::prelude::*;
+        self.inner
+            .set_active(activate)
+            .change_context(Error)
+            .attach("Failed to set_active pad")?;
+        Ok(())
+    }
+}