Support grafana links

What does this MR do?

Mentions: #217736 (closed)

User-defined links (docs) in the dashboard yml file support passing time range to the URLs (!33663 (merged)).

However, if a Grafana link is passed, the time range params are not compatible. This MR modifies the params so that it is compatible with Grafana. Grafana time modifies documentation is here

All absolute time ranges are converted to epoch and relative time ranges to now - <seconds>s.

-	Before	After
Absolute time range	{ start: 'ISOString', end: 'ISOString' }	{ from: 'epoch', to: 'epoch' }
Relative time range	{ duration_seconds: 86400 }	{ from: 'now-86400s', end: 'now' }

Demo

https://gitlab-review-support-gr-1gb5s9.gitlab-review.app/root/monitor-sandbox-2/-/environments/2/metrics?dashboard=.gitlab%2Fdashboards%2Fmany_links.yml

Sample dashboard for testing

many_links.yml

Screenshots

header	header
Relative time - Metrics dashboards	relative_time_gitlab_dashboard
Relative time - Grafana dashboards (with UTC and browser timezone)	relative_time_grafana
Absolute time - Grafana and Metrics dashboards	absolute_time_grafana_and_gitlab

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