crmMailing - Only load Angular settings if they're needed

[totten]

Overview

This removes extraneous data from Angular-based screens which do not have a CiviMail UI.

This patch was written as an exercise in reviewing #18731.

Before

• If you navigate to civicrm/a/#/mailing/1 and open a browser console, you can see that CRM.crmMailing is populated. This is good because we're on the mailing page.
• If you navigate to civicrm/admin/afform and open a browser console, you again see that CRM.crmMailing is populated. This is extraneous because crmMailing is never activated on this screen.

After

• (Same) If you navigate to civicrm/a/#/mailing/1 and open a browser console, you can see that CRM.crmMailing is populated. This is good because we're on the mailing page.
• (Changed) If you navigate to civicrm/admin/afform and open a browser console, you can see that CRM.crmMailing is not populated.

Comments

In reading the diff, it looks slightly noisier than it should. What's actually happened is that I used a refactoring (Extract Method) to move several lines from getAngularModules() to a separate function createAngularSettings(). Due to the dependence on the other PR and the quirks in diff format, it makes it appear as if some unrelated functions are removed+readded. 🤷‍♂️

[civibot]

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[colemanw]

This is good. And I have a followup PR to take care of declaring permissions from Angular modules.