Clean up shared/tmp folder after Project/Group Import/Export

What does this MR do?

After Project/Group Import/Export is complete (success or failure) ensure shared/tmp folder is cleaned up so that there are no intermediate files left.

Example of shared.base_path for Project and Group:

Project:

/.../gitlab/shared/tmp/gitlab_exports/ayaya32/h2qec/ee7os/b705n

Group:

/.../gitlab/shared/tmp/gitlab_exports/@hashed/ae/a9/aea92132c4cbeb263e6ac2bf6c183b5d81737f179f21efdc5863739672f0f470/d74ba879c8f0e91134a53325c1d674e7"

The main goal is to remove any leftover temp files after Import/Export. However, there is still a possibility for empty directories to be present.

Mentions #194193 (closed)

Screenshots

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