Refactor monitoring dashboard to allow dashboard data refresh

What does this MR do?

Related to #207549 (closed)

The most important change is to enable a single action: fetchPrometheusMetrics to "atomically" refresh the dashboard data and only the dashboard data. This will a allow a follow up MR dashboard component to use it.

Some Vuex improvements were added:

• Actions that can be replaced by simple mutations are removed in favor of their corresponding mutations.
• Mutations like REQUEST_METRICS_DATA are renamed to REQUEST_METRICS_DASHBOARD to better represent the changes being done.
• fetchDeploymentsData is called as part of the data loading of the dashboard, so they can be refreshed as well.
• The time range params for data fetching are created later in the dispatch chain, so params do not have to be passed around.

Screenshots

No UX changes.

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

Related to #207549 (closed)