Reduce database calls on CI Templates specs

What does this MR do?

Reduce database calls on CI Templates specs

This change replaces let with let_it_be to reduce unnecessary number of database calls on CI Templates specs. We also replace all instances of allow_any_instance_of stubs with allow_next_instance_off according to the Rubocop lint rules.

Before: 724 calls, 4 minutes 29.7 seconds

Finished in 4 minutes 29.7 seconds (files took 39.46 seconds to load)
204 examples, 0 failures

Randomized with seed 8506

[TEST PROF INFO] Factories usage

 Total: 724
 Total top-level: 435
 Total time: 102.0235s
 Total uniq factories: 9

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

     198         198       92.7114s            0.4682s            92.7114s            project
     198           0       17.3099s            0.0874s             0.0000s          namespace
     140         140        1.3582s            0.0097s             1.3582s            license
      80          80        1.0749s            0.0134s             1.0749s        ci_variable
      39           0        3.2725s            0.0839s             0.0000s               user
      39          13        7.5797s            0.1944s             5.1383s            cluster
      13           0        1.5845s            0.1219s             0.0000s cluster_platform_kubernetes
      13           0        1.4302s            0.1100s             0.0000s cluster_provider_gcp
       4           4        1.7406s            0.4352s             1.7406s      merge_request

After: 482 calls, 3 minutes 42.5 seconds

Finished in 3 minutes 42.5 seconds (files took 11.45 seconds to load)203 examples, 0 failures

Randomized with seed 15799

[TEST PROF INFO] Factories usage

 Total: 482
 Total top-level: 246
 Total time: 71.7134s
 Total uniq factories: 9

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

     145         145       64.2338s            0.4430s            64.2338s            project
     145           0       11.3681s            0.0784s             0.0000s          namespace
      69          69        0.8523s            0.0124s             0.8523s        ci_variable
      39          13        7.1232s            0.1826s             4.8595s            cluster
      39           0        3.0037s            0.0770s             0.0000s               user
      15          15        0.1450s            0.0097s             0.1450s            license
      13           0        1.3385s            0.1030s             0.0000s cluster_provider_gcp
      13           0        1.5114s            0.1163s             0.0000s cluster_platform_kubernetes
       4           4        1.6228s            0.4057s             1.6228s      merge_request

Does this MR meet the acceptance criteria?

Conformity

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  • I have included a changelog entry.
  • I have not included a changelog entry because this change is development-facing only.
• [-] Documentation (if required)
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• 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

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• [-] 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
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