Allow submodule contains dot in path

What does this MR do?

issue: #55373 (moved)

This MR change requirements for submodule path in API. The change applies allow use . (dot) in path/name of submodule. Test fails because, the same change should be done in Gitaly in my opinion.

This is my first MR for Gitlab and OpenSource. I will be grateful for feedback.

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.

Closes #55373 (moved)