Allow Running Container as Runner Host User (#600)

- Added `runAsHostUser` to allow running the container as the same user as the host system. This fixes most permissions issues on self-hosted runners.
- Perform android sdk setup during entrypoint.sh to ensure it has root permissions if the user switches to a non-root user
- Automatically detect android sdk target version if parameters are not already provided to configure the sdk
- Generate a new uuid for machineID to ensure separate containers are unique to reduce license activation errors
- Add exponential retry strategy for Ubuntu license activations

dist/platforms/mac/steps/activate.sh

@@ -20,10 +20,6 @@ echo "Requesting activation"
 # Store the exit code from the verify command
 UNITY_EXIT_CODE=$?
 
-if [ ! -f "/Library/Application Support/Unity/Unity_lic.ulf" ]; then
-    echo "::error ::There was an error while trying to activate the Unity license."
-fi
-
 #
 # Display information about the result
 #