feat: Add experimental rewrite of go2rtc live provider (MSE/WebRTC/MP4/MJPEG) (#2580)

- Closes #2556
- Closes #2450

**Key intended features:**
 - go2rtc compatible
- 100% test coverage to significantly improve ability to test, maintain
and work around browser weirdnesses (e.g. Safari).
 - Written from the ground up in the style of the rest of the project.

**To use:**
 - Change `live_provider` from `go2rtc` to `go2rtc-experimental`.

tests/components-lib/live/providers/go2rtc-experimental/utils/live-edge-tracker/index.test.ts

@@ -0,0 +1,17 @@
+import { describe, expect, it } from 'vitest';
+
+import { LiveEdgeTracker } from '../../../../../../../src/components-lib/live/providers/go2rtc-experimental/utils/live-edge-tracker';
+import { createStatus } from './test-utils';
+
+describe('LiveEdgeTracker', () => {
+  it('should use the seek strategy on WebKit', () => {
+    const tracker = new LiveEdgeTracker({ webkit: true });
+    // Far behind: the WebKit strategy seeks to the default 3s hold-back.
+    expect(tracker.next(createStatus(20, 13))).toEqual({ action: 'seek', seconds: 17 });
+  });
+
+  it('should use the playback-rate strategy on other browsers', () => {
+    const tracker = new LiveEdgeTracker({ webkit: false });
+    expect(tracker.next(createStatus(20, 18))).toEqual({ action: 'rate', rate: 1 });
+  });
+});