Rename Projects::ServicesController and change routes

What does this MR do and why?

Merge all actions into Projects::Settings::IntegrationsContoller, and rename the previous #show action to #index for consistency with the admin and group controllers.

The URL paths for the member actions change from /-/integrations/... to /-/settings/integrations/....

The #index action stays in /-/settings/integrations.

Also rename Projects::ServiceHookLogsController to Projects::Settings::IntegrationHookLogsController, since it's routes are now in this namespace as well.

This is part of our rename from "services" to "integrations" in &2504 (closed)

Related to #334846 (closed)

How to set up and validate locally

1. Navigate to a project
2. Navigate to Settings --> Integrations
3. Navigate to any of the integrations, enter settings and save them, and click the Test settings button

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