Speed-up tree reorder epic specs by using aggregate_failures

What does this MR do and why?

This MR improves the speed of ee/spec/services/epics/tree_reorder_service_spec.rb by using :aggregate_failures.

It also:

• Fixes all remaining 👮 offenses
• Ensure that the spec can be run in random order

See individual commit message for details.

How to set up and validate locally

bin/rspec ee/spec/services/epics/tree_reorder_service_spec.rb

RSpec Profiling

Here's the output from test-prof when run with FPROF=1. Note:

• Total amount of factories created went down from 587 to 242 🚀
• Total events went down from 13952 to 6472
• Queries saved: 7480

Before

Finished in 1 minute 5.13 seconds (files took 13.33 seconds to load)
90 examples, 0 failures

Randomized with seed 31962

[TEST PROF INFO] Time spent in factories: 00:30.643 (45.2% of total time)
[TEST PROF INFO] Factories usage

 Total: 587
 Total top-level: 338
 Total time: 00:30.643 (out of 01:15.528)
 Total uniq factories: 12

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

     226         226       26.6220s            0.1178s            26.6220s               epic
     226           0       19.1435s            0.0847s             0.0000s             author
      96          96        0.9057s            0.0094s             0.9057s         epic_issue
       8           8        0.7310s            0.0914s             0.7310s              group
       8           0        0.0454s            0.0057s             0.0000s namespace_settings
       8           0        0.0400s            0.0050s             0.0000s namespace_ci_cd_settings
       4           4        0.4277s            0.1069s             0.4277s              issue
       4           0        0.0271s            0.0068s             0.0000s     work_item_type
       2           1        0.8745s            0.4373s             0.6405s               user
       2           2        1.3031s            0.6516s             1.3031s            project
       2           0        0.2621s            0.1311s             0.0000s          namespace
       1           1        0.0138s            0.0138s             0.0138s            license

After

Finished in 31.23 seconds (files took 10.99 seconds to load)
34 examples, 0 failures

Randomized with seed 5245

[TEST PROF INFO] Time spent in factories: 00:12.675 (37.54% of total time)
[TEST PROF INFO] Factories usage

 Total: 242
 Total top-level: 137
 Total time: 00:12.675 (out of 00:40.750)
 Total uniq factories: 12

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

      88          88        9.7863s            0.1112s             9.7863s               epic
      88           0        7.2291s            0.0821s             0.0000s             author
      36          36        0.4491s            0.0125s             0.4491s         epic_issue
       5           5        0.4210s            0.0842s             0.4210s              group
       5           0        0.0248s            0.0050s             0.0000s namespace_settings
       5           0        0.0218s            0.0044s             0.0000s namespace_ci_cd_settings
       4           4        0.4827s            0.1207s             0.4827s              issue
       4           0        0.0302s            0.0076s             0.0000s     work_item_type
       2           1        0.4682s            0.2341s             0.4143s               user
       2           2        1.1097s            0.5549s             1.1097s            project
       2           0        0.1336s            0.0668s             0.0000s          namespace
       1           1        0.0128s            0.0128s             0.0128s            license

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.