Change the title of the metrics dashboard page

What does this MR do?

Add the name of the dashboard to the <title>.

Eg. if a dashboard is named sla.yml, for a first iteration and improving this aspect, we can name the <title> sla.yml · Metrics Dashboard · <name of environment> · <namespace> / <project name> · GitLab.

The default dashboard will display the text default dashboard instead of the filename used for the other dashboards.

Dashboard type	Before	After
Default	Metrics for environment · <name of environment> · <namespace> / <project name> · GitLab	Default dashboard · Metrics Dashboard · <name of environment> · <namespace> / <project name> · GitLab
Custom	Metrics for environment · <name of environment> · <namespace> / <project name> · GitLab	fileName.yml · Metrics Dashboard · <name of environment> · <namespace> / <project name> · GitLab

Issue: #214281 (closed)

Screenshots

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