Add timezone setting to metrics dashboards configuration

What does this MR do?

frontend implementation of #214370 (closed),

backend dependencies at !33120 (merged) & !34316 (merged)

Adds timezone setting to metrics dashboards. Add new component to hold the form group and select to allow timezone selection.

Note: All "front-office" changes have been merged, so once this the setting is available and changes, this feature is complete, this MR includes the corresponding changelog.

Screenshots

User can select UTC or local time:

The dashboard timezone is adjusted:

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

Mentions #214370 (closed)