Add E2E to create project snippet with multiple files

What does this MR do?

Adds a new end-to-end test to provide coverage for creating project snippets with multiple (up to 10) files.

See testcase issue gitlab-org/quality/testcases#1024 (closed)

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