Replace gRPC Backend (#10)

**Rationale:**

Having two separate servers and communication methods resulted in additional maintenance & the need to convert often between backend & frontend data types.
By moving the backend communication off of gRPC and to just use websockets it both gives more control & allows for simplification of the implementation.

#8

**Changes:**

- Replaces gRPC backend.
  - New implementation automatically handles reconnect logic
- Implements an api layer
- Migrates examples to the api layer
- Implements a proc macro to make command handling easier
- Implements unit tests for the api layer (90+% coverage)
- Implements integration tests for the proc macro (90+% coverage)

Reviewed-on: #10
Co-authored-by: Sergey Savelyev <sergeysav.nn@gmail.com>
Co-committed-by: Sergey Savelyev <sergeysav.nn@gmail.com>

api/src/messages/telemetry_definition.rs

@@ -0,0 +1,19 @@
+use crate::data_type::DataType;
+use crate::messages::RequestResponse;
+use serde::{Deserialize, Serialize};
+use uuid::Uuid;
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct TelemetryDefinitionRequest {
+    pub name: String,
+    pub data_type: DataType,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct TelemetryDefinitionResponse {
+    pub uuid: Uuid,
+}
+
+impl RequestResponse for TelemetryDefinitionRequest {
+    type Response = TelemetryDefinitionResponse;
+}