TestFileFinder: Map rake tasks to its respective specs

What does this MR do and why?

This MR adjusts the mapping of TestFileFinder (tff) in tests.yml to map rake tasks located in lib/tasks/**/*.rake to match spec/tasks/**/*_rake_spec.rb for both FOSS and EE.

It also renames some spec files (mostly by adding _rake) to match the new pattern.

See https://docs.gitlab.com/ee/ci/testing/fail_fast_testing.html how tff is used.

How to set up and validate locally

# Before on master
tff -f tests.yml $(find {,ee/}lib/tasks -name "*.rake") | wc -l
0

# After
tff -f tests.yml $(find {,ee/}lib/tasks -name "*.rake") | wc -l
65

scripts/verify-tff-mapping
tff mapping verification passed.

Two spec files don't map to any rake task:

$ diff -u mapped.txt all.txt
--- mapped.txt  2023-05-22 11:34:37.368951162 +0200
+++ all.txt     2023-05-22 11:34:49.996649049 +0200
@@ -5,7 +5,9 @@
 ee/spec/tasks/gitlab/geo_rake_spec.rb
 ee/spec/tasks/gitlab/license_rake_spec.rb
 ee/spec/tasks/gitlab/seed/data_seeder_rake_spec.rb
+ee/spec/tasks/gitlab/seed/group_seed_rake_spec.rb
 ee/spec/tasks/gitlab/spdx_rake_spec.rb
+spec/tasks/admin_mode_spec.rb
 spec/tasks/cache_rake_spec.rb
 spec/tasks/config_lint_rake_spec.rb
 spec/tasks/dev_rake_spec.rb

1. ee/spec/tasks/gitlab/seed/group_seed_rake_spec.rb: It's related to spec/tasks/gitlab/seed/group_seed_rake_spec.rb but takes EE into account. We could integrate this spec into the FOSS version and use Gitlab.ee block 🤷
2. This is testing that "admin mode" is enabled properly in any rake task. One could argue that we could replace this spec by adding a unit spec for Gitlab::Auth::CurrentUserMode and test admin_mode? differently 🤷

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.