Update jest to version 26.x

What does this MR do?

Update jest to version 26.x

Also updates all jest related dependencies to be compatible with jest@26.

Earlier versions of jest@26 had severe performance impacts, but that has been resolved with jest@26.5. 0

Thanks to this update jest-environment-jsdom-sixteen can be replaced with the upstream "jest-environment-jsdom which is also based on jsdom@16.

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