Simplified deploy/drain timeouts

Remove `stop_wait_time` and `readiness_timeout` from the root config
and remove `deploy_timeout` and `drain_timeout` from the proxy config.

Instead we'll just have `deploy_timeout` and `drain_timeout` in the
root config.

For roles that run the proxy, they are passed to the kamal-proxy deploy
command. Once that returns we can assume the container is ready to
shut down.

For other roles, we'll use the `deploy_timeout` when polling the
container to see if it is ready and the `drain_timeout` when stopping
the container.

test/configuration/validation_test.rb

@@ -14,7 +14,7 @@ class ConfigurationValidationTest < ActiveSupport::TestCase
       assert_error "#{key}: should be a boolean", **{ key => "foo" }
     end
 
-    [ :stop_wait_time, :retain_containers, :readiness_delay ].each do |key|
+    [ :deploy_timeout, :drain_timeout, :retain_containers, :readiness_delay ].each do |key|
       assert_error "#{key}: should be an integer", **{ key => "foo" }
     end