embedded stdlib

This PR embeds the stdlib into the dagger binary itself for convenience.
Long term we will want to source the stdlib directly from git.

- Updated go to 1.16 to use the new built-in embedding functionality
- The `stdlib` go package now contains an embed of the stdlib

Signed-off-by: Andrea Luzzardi <aluzzardi@gmail.com>

.github/workflows/ci.yml

@@ -14,7 +14,7 @@ jobs:
       - name: Set up Go
         uses: actions/setup-go@v1
         with:
-          go-version: 1.15.6
+          go-version: 1.16
         id: go
 
       - name: Install Dependencies