use ~/.config/dagger rather than ~/.dagger

since `.dagger` directories have a special meaning now because of gitflow,
it's better not to have a `~/.dagger` since it's not a workspace and
it confuses dagger (e.g. `dagger new` from $HOME).

We don't store state there anymore, just keys and the last version
check, so it's okay to be in ~/.config IMO

Looking at my system, in ~/.config there's `gcloud`, `gatsby`, `gh`,
`yarn`, and others so it seems like a pretty common location.

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

tests/helpers.bash

@@ -13,7 +13,7 @@ common_setup() {
     DAGGER_WORKSPACE="$(mktemp -d -t dagger-workspace-XXXXXX)"
     export DAGGER_WORKSPACE
 
-    SOPS_AGE_KEY_FILE=~/.dagger/keys.txt
+    SOPS_AGE_KEY_FILE=~/.config/dagger/keys.txt
     export SOPS_AGE_KEY_FILE
 }