Use erlef in ci

Using mise to install erlang in CI makes our CI very very slow
Painfully slow
This is because it builds erlang every single time it can't find a
cached version, which can be every build on a slower moving project.

Erlef/setup-beam, on the other hand, uses precompiled binaries wherever
possible, and is therefore much faster.

Author: paradox460

.github/workflows/ci.yaml

@@ -14,6 +14,12 @@ jobs:
     steps:
       - uses: actions/checkout@v2
       - uses: jdx/mise-action@v2
+        env:
+          MISE_ENV: ci
+      - uses: erlef/setup-beam@v1
+        with:
+          version-file: .tool-versions
+          version-type: strict
       - name: Deps Cache
         id: deps-cache
         uses: actions/cache@v3
@@ -22,8 +28,8 @@ jobs:
             deps
             _build
             .mix/archives/
-          key: test-${{hashFiles('.mise.toml')}}-${{hashFiles('mix.lock')}}
-          restore-keys: test-${{hashFiles('.mise.toml')}}-
+          key: test-${{hashFiles('.tool-versions')}}-${{hashFiles('mix.lock')}}
+          restore-keys: test-${{hashFiles('.tool-versions')}}-
       - name: Install Dependencies
         run: |
           mix local.hex --force --if-missing

.mise.ci.toml

@@ -0,0 +1,3 @@
+[settings]
+# Mise installer for elixir/erlang is _slooow_, so we use erlef/setup-beam to get tool versions instead
+disable_tools = ['elixir', 'erlang']

.mise.toml

@@ -0,0 +1,3 @@
+rust   1.78.0
+elixir 1.17.2-otp-27
+erlang 27.0.1