Re-add graphql configuration

What does this MR do and why?

rubocop-graphql was accidentally removed in !205 (merged).

See !205 (comment 1841947772) and !214 (comment 1841879892).

This MR also moves require statements to corresponding configuration files.

How to verify locally

bundle exec rubocop --show-cops > after.txt
git checkout master
bundle exec rubocop --show-cops > before.txt

diff -u before.txt after.txt

--- before.txt	2024-04-02 17:13:26.563038431 +0200
+++ after.txt	2024-04-02 17:14:46.989795323 +0200
@@ -535,7 +535,7 @@
 
 # Department 'GraphQL' (21):
 GraphQL/ArgumentDescription:
-  Enabled: true
+  Enabled: false
   VersionAdded: '0.80'
   Description: Ensures all arguments have a description
 
@@ -550,7 +550,7 @@
   Description: This cop enforces arguments to be defined once per block
 
 GraphQL/ExtractInputType:
-  Enabled: true
+  Enabled: false
   VersionAdded: '0.80'
   Description: Suggests using input type instead of many arguments
   MaxArguments: 2
@@ -558,7 +558,7 @@
   - "**/graphql/mutations/**/*.rb"
 
 GraphQL/ExtractType:
-  Enabled: true
+  Enabled: false
   VersionAdded: '0.80'
   Description: Suggests extracting fields with common prefixes to the separate type
   MaxFields: 2
@@ -581,7 +581,7 @@
   - define_resolver_after_definition
 
 GraphQL/FieldDescription:
-  Enabled: true
+  Enabled: false
   VersionAdded: '0.80'
   Description: Ensures all fields have a description
 
@@ -610,7 +610,7 @@
   Description: This cop enforces fields to be defined once
 
 GraphQL/LegacyDsl:
-  Enabled: true
+  Enabled: false
   VersionAdded: '0.80'
   Description: Checks that types are defined with class-based API
 
@@ -620,7 +620,7 @@
   Description: Ensures that fields with multiple definitions are grouped together
 
 GraphQL/ObjectDescription:
-  Enabled: true
+  Enabled: false
   VersionAdded: '0.80'
   Description: Ensures all types have a description
   Exclude:

Some rules related to GraphQL as disabled again as per https://gitlab.com/gitlab-org/ruby/gems/gitlab-styles/-/blob/master/rubocop-graphql.yml?ref_type=heads.