Move core actions to a subpackage

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

tests/plan/client/filesystem/write/test.cue

@@ -2,6 +2,7 @@ package main
 
 import (
 	"dagger.io/dagger"
+	"dagger.io/dagger/core"
 )
 
 dagger.#Plan & {
@@ -15,30 +16,30 @@ dagger.#Plan & {
 	}
 
 	actions: {
-		image: dagger.#Pull & {
+		image: core.#Pull & {
 			source: "alpine:3.15.0@sha256:e7d88de73db3d3fd9b2d63aa7f447a10fd0220b7cbf39803c803f2af9ba256b3"
 		}
 		test: {
-			fs: data: dagger.#WriteFile & {
+			fs: data: core.#WriteFile & {
 				input:    dagger.#Scratch
 				path:     "/test"
 				contents: "foobar"
 			}
 			file: {
 				// Only using contents for reference in client
-				data: dagger.#WriteFile & {
+				data: core.#WriteFile & {
 					input:    dagger.#Scratch
 					path:     "/test"
 					contents: "foobaz"
 				}
 			}
 			secret: {
-				create: dagger.#WriteFile & {
+				create: core.#WriteFile & {
 					input:    dagger.#Scratch
 					path:     "/test"
 					contents: "foo-barab-oof"
 				}
-				data: dagger.#NewSecret & {
+				data: core.#NewSecret & {
 					input: create.output
 					path:  "/test"
 				}