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/windows/activate.ps1

@@ -13,7 +13,4 @@ Write-Output ""
                                      -projectPath "c:/BlankProject" `
                                      -logfile - | Out-Host
 
-if(-not(Test-path "C:/ProgramData/Unity/Unity_lic.ulf" -PathType leaf))
-{
-  Write-Output "::error ::There was an error while trying to activate the Unity license."
-}
+$ACTIVATION_EXIT_CODE = $LASTEXITCODE