Blackfire in Lando (alternate approach)

[rbayliss]

This PR is another way of running Blackfire in Lando that I think might be more stable. Blackfire actually has 3 parts:

• Probe (installed as a PHP extension)
• CLI (just a binary you invoke over the command line).
• Agent (a service that must be running for the above to work).

Currently in #109, all 3 are running in the app server. This PR switches things up so that the agent runs in another container, and the probe and CLI are installed on the server. The advantage here is that you don't have to make sure the agent is running on the app server (something that appears to be problematic from the comments).

I'm not actually sure how to configure this with a .env directory, but you just need to make the 4 blackfire environment variables available when lando is started, either by putting them into a .env file or exposing them manually. Also, just a note on that .env directory - I found that a bit confusing, since I'd normally have a .env file, and I can't anymore. If those configurations are meant to be shared, it'd be awesome to move them into the .lando directory with the other configuration so you can retain a top level .env file.

[jlandfried]

Makes sense, yeah I'm a factor of moving .env/ to .lando/ also, that sounds good. Thanks for this!