Adding Layer to support Symfony Runtime component

[Nyholm]

This may be premature, but I wrote the code and pushed a layer here: arn:aws:lambda:eu-central-1:403367587399:layer:bref-symfony-runtime:3

Here is some information about code that I think should eventually move into Bref itself: https://github.com/php-runtime/bref
Here is a small Symfony example application: https://github.com/Nyholm/bref-runtime-demo

See this PR more as a discussion rather than "Merge this now".

With this PR you are able to run any PHP application on Bref by:

composer install runtime/bref

 # serverless.yml

 functions:
     web:
         handler: public/index.php
         timeout: 10
         layers:
-            - ${bref:layer.php-80}
+            - ${bref:layer.php-80-runtime}

Benefits includes:

• We can solve the timeout problem (started in Handle timeouts more gracefully by allowing the application to shutdown #895)
• Automatically handle "trusted proxies" in Symfony and Laravel applications. (source)
• No need for special layer for FPM, Console or FPM-dev. Ie less choices.

[Nyholm]

FYI 1: I added brefphp/extra-php-extensions#231

FYI 2: I'll do a big presentation about this on Symfony Online in about 4 weeks.

[mnapoli]

Hey @Nyholm, adding that in bref-extra sounds like a good solution for now! At least the layer is available/usable, which is great to gauge usefulness and adoption.

[mnapoli]

🎉 Symfony runtime is now implemented and supported in https://github.com/brefphp/symfony-bridge

I've released a beta version, there should be a stable in the coming weeks!