Move core actions to a subpackage

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

tests/tasks/trimsecret/trimsecret.cue

@@ -2,30 +2,31 @@ package main
 
 import (
 	"dagger.io/dagger"
+	"dagger.io/dagger/core"
 )
 
 dagger.#Plan & {
 	actions: {
-		image: dagger.#Pull & {
+		image: core.#Pull & {
 			source: "alpine:3.15.0@sha256:e7d88de73db3d3fd9b2d63aa7f447a10fd0220b7cbf39803c803f2af9ba256b3"
 		}
 
-		generate: dagger.#Exec & {
+		generate: core.#Exec & {
 			input: image.output
 			args: ["sh", "-c", "echo ' test ' > /secret"]
 		}
 
-		load: dagger.#NewSecret & {
+		load: core.#NewSecret & {
 			input:     generate.output
 			trimSpace: false
 			path:      "/secret"
 		}
 
-		trim: dagger.#TrimSecret & {
+		trim: core.#TrimSecret & {
 			input: load.output
 		}
 
-		verify: dagger.#Exec & {
+		verify: core.#Exec & {
 			input: image.output
 			mounts: secret: {
 				dest:     "/run/secrets/test"