Improve CI build with installation/integration test

[asgrim]

We recently implemented a full installation into a Laravel application of the scout-apm-laravel library to be built to ensure the key happy path functions as expected (i.e. automatic integration into the framework).

See: https://github.com/scoutapp/scout-apm-laravel/blob/2972870c3067a938f1b5435c4cf7a1dc80bff7fd/.github/workflows/build.yml#L10-L65

We should implement a similar CI step into the scout-apm-symfony-bundle that sets up a Symfony application, installs scout-apm-symfony-bundle, and performs a check to ensure we send the payload to the core-agent as we expect.