Refactor Rails initializers

We currently have 100+ initializers in config/initializers. These are loaded by Rails alphabetically so ordering is important.

We have a few of them that are numbered to force the order but they are inconsistent and there are duplicate numbers. 01_.., 1_.., etc..

This has caused a bug here: https://gitlab.com/gitlab-org/gitlab-ce/issues/55513

We should name these consistently and perhaps make it easier to insert initializers in between without having to rename a bunch of files.

We should also consider reducing the number of files here.