Add button to synchronize all execution environments

This adds a button to the execution environment index page that, when
clicked, causes all execution environments to be synchronized to the
runner management (Poseidon) by creating or replacing them.

CodeOcean does not synchronize it's execution environments on startup or
when a new runner management configuration is used for the first time.
The administrator has to manually start this process by pressing this
button.

The equivalent for syncing just one execution environment is updating
it.

app/controllers/execution_environments_controller.rb

@@ -164,6 +164,19 @@ class ExecutionEnvironmentsController < ApplicationController
     end
   end
 
+  def synchronize_all_to_poseidon
+    authorize ExecutionEnvironment
+
+    return unless RUNNER_MANAGEMENT_PRESENT
+
+    success = ExecutionEnvironment.all.map(&:copy_to_poseidon).all?
+    if success
+      redirect_to ExecutionEnvironment, notice: t('execution_environments.index.synchronize_all.success')
+    else
+      redirect_to ExecutionEnvironment, alert: t('execution_environments.index.synchronize_all.failure')
+    end
+  end
+
   def copy_execution_environment_to_poseidon
     unless RUNNER_MANAGEMENT_PRESENT && @execution_environment.copy_to_poseidon
       t('execution_environments.form.errors.not_synced_to_poseidon')