remove test_pr and run test_linux on all prs and main

Author: kalleep

.github/workflows/test_full.yml renamed to .github/workflows/test_linux.yml

@@ -1,15 +1,16 @@
-name: Test (Full)
+name: Test (Linux)
 on:
   push:
     branches:
       - main
+  pull_request:
 
 permissions:
   contents: read
 
 jobs:
   test_linux:
-    name: Test (Full)
+    name: Test Linux
     runs-on: ubuntu-latest-8-cores
     container:
       image: grafana/alloy-build-image:v0.1.21@sha256:36b1e621f32f46aa1de58843b885f0885faabe7b29468462d36a60bea1245e33
@@ -29,6 +30,4 @@ jobs:
       uses: actions/setup-go@d35c59abb061a4a6fb18e82ac0862c26744d6ab5 # v5.5.0
       with:
         go-version-file: go.mod
-        # TODO: Enable caching later.
-        cache: false
     - run: K8S_USE_DOCKER_NETWORK=1 make test