Hashed Storage: make migration and rollback resilient to exceptions

What does this MR do?

Hashed Storage migration was failing for some users due to exceptions being triggered by Gitaly or Encrypted Attributes (due to corrupted keys at somepoint).

This adds two exception handling points to migration and rollback operation to prevent any of the exceptions above to let the project into an inconsistent state (folders moved but database still pointing to previous version).

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

Related to #259605 (closed)