WIP: Downstream pipelines UX improvements

What does this MR do?

• Adds a Mutli-project label to a downstream pipeline just like the Child label for downstream child pipelines.
• Updated the tooltip text to include data on what job actually triggered the child pipeline.
• Remove tooltips on Child and new Multi-project labels
• Update the title of child pipelines to always be child-pipeline

Screenshots

New Labels

Tooltip text

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