Speed up project specs

What does this MR do?

Not much but this shoves off some db creations from the project spec, mostly using let_it_be or build/build_stubbed where possible.

EVENT_PROF='sql.active_record' bundle exec rspec spec/models/project_spec.rb

Before

Total time: 00:59.752 of 02:06.227 (47.34%)
Total events: 72811

After

Total time: 00:54.303 of 01:54.540 (47.41%)
Total events: 63649

Queries saved: 9162

Screenshots

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