[Dev] Fix CI caching (#325)

* Consolidated dockerfile commands

* Added teardown step

* FIxed typo

* Got rid of old caching action

* Added buildx

* Added steps for compiling test ENV to dockerfile

* Changed the order of things

* Added env vars

* more env vars

* Removed step

* No compile flag

* fetch quest

* Removed other thing

* volumes

* Rolling back some other changes

* more consolidation

* updated checkout runner

docker-compose.ci.yml

@@ -7,6 +7,9 @@ services:
       - MIX_ENV=test
     volumes:
       - '.:/app'
+      # These lines ensure the deps can be saved as build artifacts for caching
+      - '/app/deps'
+      - '/app/_build'
     ports:
       - '4008:4008'
     command: tail -F /dev/null