Use shared EmulatorRunner from android-tools for BootAndroidEmulator

Replace the 454-line BootAndroidEmulator implementation with a thin
~180-line wrapper that delegates to EmulatorRunner.BootEmulatorAsync()
from Xamarin.Android.Tools.AndroidSdk.

Key changes:
- Remove all process management, polling, and boot detection logic
- Delegate to EmulatorRunner.BootEmulatorAsync() for the full 3-phase
  boot: check online → check AVD running → launch + poll + wait
- Map EmulatorBootResult errors to existing XA0143/XA0145 error codes
- Virtual ExecuteBoot() method for clean test mocking
- Update submodule to feature/emulator-runner (d8ee2d5)

Tests updated from 9 to 10 (added ExtraArguments and UnknownError tests)
using simplified mock pattern — MockBootAndroidEmulator overrides
ExecuteBoot() to return canned EmulatorBootResult values.

Depends on: dotnet/android-tools#284

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: rmarinho