Add a constraint on the query parameter to allow querying for projects with dots in their name.

What does this MR do?

Current API doesn't allow querying projects with dot(s) in the name

Are there points in the code the reviewer needs to double check?

This is a trivial change: Added a constraint to the query parameter to prevent a dot from being used as a separator.

Why was this MR needed?

Without the change, a query like the following

http://..........//api/v3/projects/search/one.dot

is interpreted as

http://..........//api/v3/projects/search/one

Clearly not the intended behavior

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/25558