Allow destination and config-file in aliases

We only loaded the configuration once, which meant that aliases always
used the initial configuration file and destination.

We don't want to load the configuration in subcommands as it is not
passed all the options we need. But just checking if we are in a
subcommand is enough - the alias reloads and the subcommand does not.

One thing to note is that anything passed on the command line overrides
what is in the alias, so if an alias says
`other_config: config -c config/deploy2.yml` and you run
`kamal other_config -c config/deploy.yml`, it won't switch.

test/cli/build_test.rb

@@ -274,17 +274,4 @@ class CliBuildTest < CliTestCase
       SSHKit::Backend::Abstract.any_instance.stubs(:execute)
         .with { |*args| args[0..1] == [ :docker, :buildx ] }
     end
-
-    def with_build_directory
-      build_directory = File.join Dir.tmpdir, "kamal-clones", "app-#{pwd_sha}", "kamal"
-      FileUtils.mkdir_p build_directory
-      FileUtils.touch File.join build_directory, "Dockerfile"
-      yield build_directory + "/"
-    ensure
-      FileUtils.rm_rf build_directory
-    end
-
-    def pwd_sha
-      Digest::SHA256.hexdigest(Dir.pwd)[0..12]
-    end
 end