Add AVD Manager wrapper (avdmanager CLI)

[rmarinho]

Summary

Add AvdManagerRunner class to Xamarin.Android.Tools.AndroidSdk to wrap avdmanager CLI operations for programmatic AVD management.

Background

The MAUI DevTools CLI needs to create, delete, and list Android Virtual Devices. This functionality should live in the shared android-tools package so it can be reused by VS, VS Code extensions, and CLI tools.

Reference implementation exists in android-platform-support (internal) Mono.AndroidTools.AvdManager.

Proposed API Surface

`csharp
public class AvdManagerRunner
{
Task<IReadOnlyList> ListAvdsAsync(CancellationToken ct = default);
Task CreateAvdAsync(string name, string device, string systemImage, CancellationToken ct = default);
Task DeleteAvdAsync(string name, CancellationToken ct = default);
}

public record AvdInfo(string Name, string Device, string Path, string Target, string Abi);
`

Consumer

• MAUI DevTools CLI (maui android emulator create/delete/list) — see MAUI DevTools Spec PR

Related

• Add SDK bootstrap and sdkmanager wrapper (move from android-platform-support) #271 (SDK bootstrap)
• Add SDK license acceptance support (move from android-platform-support) #272 (License acceptance)
• MAUI DevTools spec §6.8: Shared Libraries & Code Reuse