Enable Layout/TrailingWhitespace cop and auto-correct offenses

See merge request !13573

Fix CI_PROJECT_PATH_SLUG slugify

Closes #34643

See merge request !13350

Don't depend on `Rails` for Redis configuration file paths

Closes #36514

See merge request !13575

Speed up project creation by inlining repository creation

Closes #34533

See merge request !13529

The `Rails` object was not always available in all tasks that require
Redis access, such as `mail_room`, so the constant pointing to the
configuration path was never defined, but we still attempted to access
it in `config_file_name`, resulting in a `NameError` exception.

Further, there was no benefit to defining these paths in a constant to
begin with -- they're only accessed in one place, and it was within the
class where they were being defined. We can just provide them at
run-time instead.

Further _still_, we were calling `File.expand_path` on the absolute path
returned by `Rails.root.join`, which was rather pointless.

Remove deprecated field from workhorse API responses

See merge request !13567

Related to !13108. Mostly this is just running the rake task and
changing the task a bit to catch cases like the project already existing
or so. The rake task moves archives to the vendor/project_template
directory, which are checked in too.