Align BitBucket Server import name validation criteria with GitLab

What does this MR do and why?

It allows the BitBucket Server importer to import repos that have a space in their name.

It makes sure the GitLab ProjectsCreator uses the repo slug for the GitLab project path (instead of the repo name).

Screenshots or screen recordings

Successful import of test repo (path: test-repo)

BBS

GL

How to set up and validate locally

1. Create a BBS project and repo with a space in its name

2. Use the GitLab BBS importer to import the repo

3. Import fails with

   {"error":"Path can contain only letters, digits, '_', '-' and '.'. Cannot start with '-', end in '.git' or end in '.atom'"}

4. Apply MR change and import again, import succeeds

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #325099