Conditionally render gfm metrics

What does this MR do?

render_metrics.js file loads on all pages, which I believe is correct. However, that also loads the Vuex store from monitoring/stores/embed_group before any other store on a page. Because of this only the embedGroup store and getters are visible on the Vuex chrome developer tools.

This MR changes the embed_group store so that it is initialized when the components/embeds/embed_group.vue component is loaded.

Screenshots

Before	After

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• [-] Style guides
• [-] Database guides
• [-] Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team