Add ADB file push support for device file operations

[rmarinho]

Summary

Add support for pushing content/files to a device via ADB, enabling the MAUI DevTools CLI to write files to connected devices without going through ServiceHub.

Context

The VS Code MAUI extension currently uses the C# ServiceHub (AndroidDeviceManager.createFile()) to push files to Android devices. This is used during debugging to write XAML Hot Reload environment variables to the device filesystem. As part of the ServiceHub → CLI migration, we need this as a library API.

What the ServiceHub does today

From Microsoft.VisualStudio.Maui.Devices:

• createFile(deviceSerial, remotePath, content) → writes content to a temp file, then runs adb -s <serial> push <tempFile> <remotePath>

Consumer

• VS Code extension: MauiAndroidPlatform.ts → setXamlToolsEnvironmentVariables() (writes env config file to device for XAML Hot Reload)

Proposed API

Add to AdbRunner:

`csharp
// Push a local file to the device
Task PushFileAsync(string deviceSerial, string localPath, string remotePath, CancellationToken ct = default);

// Push string content to a remote path (writes to temp file, pushes, cleans up)
Task PushContentAsync(string deviceSerial, string content, string remotePath, CancellationToken ct = default);

// Pull a file from the device (optional, nice-to-have)
Task PullFileAsync(string deviceSerial, string remotePath, string localPath, CancellationToken ct = default);
`

CLI Command (downstream in dotnet/maui)

Once the API exists here, the MAUI DevTools CLI will expose:
maui android adb push --device <serial> --remote-path <path> --content "..." --json maui android adb push --device <serial> --remote-path <path> --local-path <file> --json

Related

• Add ADB track-devices support for efficient device monitoring #302 — ADB track-devices support
• Add ADB reverse port forwarding support #303 — ADB reverse port forwarding
• ServiceHub migration tracking in vscode-maui (dev/rumar/android-maui-tool branch)