Move core actions to a subpackage

Signed-off-by: Helder Correia <174525+helderco@users.noreply.github.com>

docs/tests/core-concepts/container-images/simple/with-dockerfile.cue

@@ -2,12 +2,13 @@ package main
 
 import (
 	"dagger.io/dagger"
+	"universe.dagger.io/docker"
 )
 
 dagger.#Plan & {
 	client: filesystem: "./src": read: contents: dagger.#FS
 
-	actions: build: dagger.#Dockerfile & {
+	actions: build: docker.#Dockerfile & {
 		// This is the context.
 		source: client.filesystem."./src".read.contents
 

docs/tests/core-concepts/plan/structure.cue.fragment

@@ -23,7 +23,7 @@ dagger.#Plan & {
       run: bash.#Run & {
          // ...
       }
-      contents: dagger.#Subdir & {
+      contents: core.#Subdir & {
         // ...
       }
     }

docs/tests/core-concepts/secrets/plans/file.cue

@@ -5,7 +5,7 @@ dagger.#Plan & {
 		contents: dagger.#Secret
 	}
 	actions: {
-		registry: dagger.#TrimSecret & {
+		registry: core.#TrimSecret & {
 			input: client.filesystem.".registry".read.contents
 		}
 		pull: docker.#Pull & {

docs/tests/core-concepts/secrets/plans/sops.cue

@@ -7,7 +7,7 @@ dagger.#Plan & {
 
 	actions: {
 		// Makes the yaml keys easily accessible
-		secrets: dagger.#DecodeSecret & {
+		secrets: core.#DecodeSecret & {
 			input:  client.commands.sops.stdout
 			format: "yaml"
 		}

docs/use-cases/1211-go-docker-swarm.md

@@ -28,6 +28,7 @@ package particubes
 
 import (
   "dagger.io/dagger"
+  "dagger.io/dagger/core"
   "universe.dagger.io/docker"
 )
 
@@ -63,7 +64,7 @@ dagger.#Plan & {
         image: build.output
       }
 
-      docsSecrets: dagger.#DecodeSecret & {
+      docsSecrets: core.#DecodeSecret & {
         input: inputs.secrets.docs.contents
         format: "yaml"
       }