[Mobile] Add BrowserStack Android MAUI Test (#23383)
### Description
Add test project that will perform an automated UI test that runs the
unit tests on Android.
### Motivation
- Enables end-to-end on-device MAUI unit testing which we want to add to
the packaging pipelines
### Context
Microsoft.ML.OnnxRuntime.Tests.MAUI uses DeviceRunners.VisualRunners to
allow running the unit tests (found in
Microsoft.ML.OnnxRuntime.Tests.Common) across multiple devices.
DeviceRunners.VisualRunners provides a simple UI with a button that will
run the unit tests and a panel with the unit test results.
In order to automate the process of running the unit tests across mobile
devices, Appium is used for UI testing orchestration (it provides a way
to interact with the UI), and BrowserStack automatically runs these
Appium tests across different mobile devices.
This project does not include the capability to start an Appium server
locally or attach to a local emulator or device.
## Build & run instructions
### Requirements
* A BrowserStack account with access to App Automate
* You can set BrowserStack credentials as environment variables as shown
[here](https://www.browserstack.com/docs/app-automate/appium/getting-started/c-sharp/nunit/integrate-your-tests#CLI)
* ONNXRuntime NuGet package
1. You can either download the [stable NuGet
package](https://www.nuget.org/packages/Microsoft.ML.OnnxRuntime) then
follow the instructions from [NativeLibraryInclude.props
file](../Microsoft.ML.OnnxRuntime.Tests.Common/NativeLibraryInclude.props)
to use the downloaded .nupkg file
2. Or follow the [build
instructions](https://onnxruntime.ai/docs/build/android.html) to build
the Android package locally
* The dotnet workloads for maui and maui-android, which will not always
automatically install correctly
1. `dotnet workload install maui`
2. `dotnet workload install maui-android`
* [Appium](https://appium.io/docs/en/latest/quickstart/) and the
[UiAutomator2
driver](https://appium.io/docs/en/latest/quickstart/uiauto2-driver/)
### Run instructions
1. Build the Microsoft.ML.OnnxRuntime.Tests.MAUI project into a signed
APK.
1. Run the following: `dotnet publish -c Release -f net8.0-android` in
the Microsoft.ML.OnnxRuntime.Tests.MAUI directory.
2. Search for the APK files generated. They should be located in
`bin\Release\net8.0-android\publish`.
3. If they're in a different location, edit the `browserstack.yml` file
to target the path to the signed APK.
2. Ensure you've set the BrowserStack credentials as environment
variables.
3. Run the following in the
Microsoft.ML.OnnxRuntime.Tests.Android.BrowserStack directory: `dotnet
test`
4. Navigate to the [BrowserStack App Automate
dashboard](https://app-automate.browserstack.com/dashboard/v2/builds) to
see your test running!
