…st stubs

This commit completely revamps the `mesh_service_example` application, migrating it from an XML-based layout to a modern, feature-rich UI built with Jetpack Compose. It also introduces a `FakeIMeshService` stub to facilitate easier testing of `IMeshService` integrations.

### Key Changes:

- **Compose UI Rewrite:** The `mesh_service_example` has been rewritten using Jetpack Compose, featuring a `MeshServiceViewModel` to manage state and interactions with the `MeshService`. The new UI demonstrates a wider range of `IMeshService` functionalities, including:
    - Displaying node information and connection status.
    - Sending and receiving broadcast text messages.
    - Requesting actions per-node (Traceroute, Telemetry, Position, etc.).
    - Controlling local device functions (Start/Stop GPS, Reboot Radio).

- **`FakeIMeshService` Stub:**
    - Introduced `FakeIMeshService`, a stub implementation of the `IMeshService` AIDL interface.
    - This fake serves as a reliable test double for developers building apps that interact with the Meshtastic service, enabling robust unit testing without a running service.
    - Added a contract test (`IMeshServiceContractTest`) to ensure the fake implementation stays in sync with the AIDL definition.

- **ViewModel and Testing:**
    - `MeshServiceViewModel` now encapsulates all logic for interacting with the `IMeshService`.
    - Unit tests for the `MeshServiceViewModel` have been added, demonstrating how to use `FakeIMeshService` for testing client-side logic.

- **Build & Dependency Updates:**
    - Added Compose, Activity Compose, and other related UI dependencies to the example app.
    - Enabled `unitTests.isReturnDefaultValues = true` in `core/service` and `mesh_service_example` to support Robolectric-less unit testing.
    - Removed the unused OSMDroid dependency from the example.

Signed-off-by: James Rich <2199651+jamesarich@users.noreply.github.com>