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/utils/websocket-url.test.ts

@@ -0,0 +1,38 @@
+import { describe, expect, it } from 'vitest';
+
+import { convertToWebSocketURL } from '../../src/utils/websocket-url';
+
+// @vitest-environment jsdom
+describe('convertToWebSocketURL', () => {
+  it('should convert http to ws', () => {
+    expect(convertToWebSocketURL('http://host:1984/api/ws?src=camera')).toBe(
+      'ws://host:1984/api/ws?src=camera',
+    );
+  });
+
+  it('should convert https to wss', () => {
+    expect(convertToWebSocketURL('https://host/api/ws?src=camera')).toBe(
+      'wss://host/api/ws?src=camera',
+    );
+  });
+
+  it('should convert a mixed-case scheme', () => {
+    expect(convertToWebSocketURL('HtTp://host/api/ws')).toBe('ws://host/api/ws');
+  });
+
+  it('should prepend the provided origin to a relative path', () => {
+    expect(convertToWebSocketURL('/api/ws?src=camera', 'https://ha:8123')).toBe(
+      'wss://ha:8123/api/ws?src=camera',
+    );
+  });
+
+  it('should prepend the location origin to a relative path by default', () => {
+    expect(convertToWebSocketURL('/api/ws?src=camera')).toBe(
+      'ws://localhost:3000/api/ws?src=camera',
+    );
+  });
+
+  it('should leave other schemes untouched', () => {
+    expect(convertToWebSocketURL('ws://host/api/ws')).toBe('ws://host/api/ws');
+  });
+});