Display error message in codeclimate widget when base_path is null

What does this MR do?

When there is no codequality artifact available for the base pipeline of a merge request, in the codequality MR widget, display Failed to load codeclimate report along with a question mark icon which displays Base pipeline codequality artifact not found on hover.

Technically, this MR

• changes shouldRenderCodeQuality() to return true even when base_path is null in order to display the MR widget
• sets the loadingCodequalityFailed flag to true when base_path is null to show the existing error message inside the widget
• adds a popover prop to the codequality <report-section /> specifically when base_path is null in order to show a question mark icon with a popover that displays the more specific error message and a link to the docs

Screenshots

before	[codeclimate widget was not displayed at all]
after
after (hover)

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

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: #14033 (closed)