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/bounded-buffer-queue.test.ts

@@ -0,0 +1,64 @@
+import { describe, expect, it } from 'vitest';
+
+import { BoundedBufferQueue } from '../../../../../../src/components-lib/live/providers/go2rtc-experimental/utils/bounded-buffer-queue';
+
+describe('BoundedBufferQueue', () => {
+  it('should start empty', () => {
+    expect(new BoundedBufferQueue(10).isEmpty).toBe(true);
+  });
+
+  it('should accept a chunk within the byte cap', () => {
+    const queue = new BoundedBufferQueue(10);
+    expect(queue.push(new ArrayBuffer(4))).toBe(true);
+    expect(queue.isEmpty).toBe(false);
+  });
+
+  it('should accept a chunk that fills the cap exactly', () => {
+    expect(new BoundedBufferQueue(10).push(new ArrayBuffer(10))).toBe(true);
+  });
+
+  it('should reject a chunk that would exceed the byte cap and stage nothing', () => {
+    const queue = new BoundedBufferQueue(10);
+    expect(queue.push(new ArrayBuffer(8))).toBe(true);
+    expect(queue.push(new ArrayBuffer(3))).toBe(false);
+
+    // The rejected chunk left the byte total unchanged, so a smaller one fits.
+    expect(queue.push(new ArrayBuffer(2))).toBe(true);
+  });
+
+  it('should return staged chunks oldest first', () => {
+    const queue = new BoundedBufferQueue(10);
+    const first = new ArrayBuffer(2);
+    const second = new ArrayBuffer(3);
+    queue.push(first);
+    queue.push(second);
+
+    expect(queue.shift()).toBe(first);
+    expect(queue.shift()).toBe(second);
+    expect(queue.isEmpty).toBe(true);
+  });
+
+  it('should return null when shifting an empty queue', () => {
+    expect(new BoundedBufferQueue(10).shift()).toBeNull();
+  });
+
+  it('should free the shifted chunk bytes back toward the cap', () => {
+    const queue = new BoundedBufferQueue(10);
+    queue.push(new ArrayBuffer(8));
+    expect(queue.push(new ArrayBuffer(4))).toBe(false);
+
+    queue.shift();
+    expect(queue.push(new ArrayBuffer(4))).toBe(true);
+  });
+
+  it('should reset the chunks and the byte total on clear', () => {
+    const queue = new BoundedBufferQueue(10);
+    queue.push(new ArrayBuffer(8));
+    queue.clear();
+
+    expect(queue.isEmpty).toBe(true);
+
+    // The byte total reset too, so the full cap is available again.
+    expect(queue.push(new ArrayBuffer(10))).toBe(true);
+  });
+});