Set project path on localStorage during onboarding

What does this MR do?

This is one of many small MRs for the new user onboarding feature, see https://gitlab.com/gitlab-org/gitlab-ce/issues/60093.

During one part of the new user onboarding, users will be guided through the process of creating a project (besides other things).

This MR sets the project path (createdProjectPath) on the onboarding's local storage object (onboarding_state), when users create a new project in the context of the onboarding tour. This is necessary as we need to read the project path of the newly create project (createdProjectPath) later in the onboarding.

In addition, it removes the onboarding's local storage object when the onboarding ist dismissed by the user.

CE Port: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/29989

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance 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