Optimize pipeline entity spec

What does this MR do?

This cuts the spec execution time in half for the pipeline entity spec by reducing the number of times we create a project.

This also moves test setup to where it's used if it's only needed in a few tests.

Test prof output:

[TEST PROF INFO] Factories usage

 Total: 87
 Total top-level: 43
 Total time: 8.6029s
 Total uniq factories: 8

   total   top-level     total time      time per call      top-level time               name

      23           9        5.2574s            0.2286s             3.0683s            project
      22           0        0.9145s            0.0416s             0.0000s          namespace
      17           9        0.4465s            0.0263s             0.2711s        ci_pipeline
       9           9        0.4255s            0.0473s             0.4255s           ci_build
       8           8        3.7470s            0.4684s             3.7470s      merge_request
       6           6        1.0407s            0.1735s             1.0407s  ci_empty_pipeline
       1           1        0.0103s            0.0103s             0.0103s            license
       1           1        0.0401s            0.0401s             0.0401s               user

[TEST PROF INFO] Factories usage

 Total: 47
 Total top-level: 26
 Total time: 3.8649s
 Total uniq factories: 8

   total   top-level     total time      time per call      top-level time               name

      11           2        2.1298s            0.1936s             0.6437s            project
      10           0        0.4647s            0.0465s             0.0000s          namespace
       9           9        0.4728s            0.0525s             0.4728s           ci_build
       7           5        0.4357s            0.0622s             0.3794s        ci_pipeline
       6           6        1.1342s            0.1890s             1.1342s  ci_empty_pipeline
       2           2        1.1788s            0.5894s             1.1788s      merge_request
       1           1        0.0464s            0.0464s             0.0464s               user
       1           1        0.0096s            0.0096s             0.0096s            license

Screenshots (strongly suggested)

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