WIP integration with sdk-test-proxy

TODO can we decrease the 1m 35s this takes to start?
TODO can we reduce the risk of one test case or test run contaminating another?

Resolves #1003.

.github/workflows/emulate.yml

@@ -16,13 +16,18 @@ jobs:
             excludeModules: true
     steps:
       - uses: actions/checkout@v3
+        with:
+          submodules: recursive
 
       # Gradle 7 requires Java 11 to run
       - uses: actions/setup-java@v3
         with:
           distribution: zulu
           java-version: '19'
 
+      - name: Start SDK test proxy server
+        run: cd external/sdk-test-proxy && ./start-service
+
       - uses: reactivecircus/android-emulator-runner@v2
         with:
           api-level: ${{ matrix.api-level }}

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "external/sdk-test-proxy"]
+	path = external/sdk-test-proxy
+	url = git@github.com:ably/sdk-test-proxy.git

android-test-common/build.gradle

@@ -6,6 +6,8 @@ plugins {
     id 'com.android.library'
     id 'kotlin-android'
     id 'org.jlleitschuh.gradle.ktlint'
+    // TODO should this be here?
+    id 'org.jetbrains.kotlin.plugin.serialization' version "$kotlin_version"
 }
 
 dependencies {
@@ -21,6 +23,8 @@ dependencies {
     implementation "io.ktor:ktor-client-logging:$ktor_version"
     implementation "uk.uuid.slf4j:slf4j-android:1.7.36-0"
 
+    implementation 'org.jetbrains.kotlinx:kotlinx-serialization-json:1.4.1'
+
     implementation 'org.msgpack:msgpack-core:0.9.3'
 }