Improve memory consumption of issuable APIs

Disables method replacement when batch loading because we don't need
or use all the methods in Struct and this leads to a lot of memory
allocations.

Changelog: performance
MR: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/61561

changelogs/unreleased/211373-improve-issues-list-api-memory.yml

+---
+title: Improve memory consumption of issuable APIs
+merge_request: 61561
+author:
+type: performance

lib/api/entities/issuable_entity.rb

@@ -24,7 +24,7 @@ module API
       # entity according to the current top-level entity options, such
       # as the current_user.
       def lazy_issuable_metadata
-        BatchLoader.for(object).batch(key: [current_user, :issuable_metadata]) do |models, loader, args|
+        BatchLoader.for(object).batch(key: [current_user, :issuable_metadata], replace_methods: false) do |models, loader, args|
           current_user = args[:key].first
 
           issuable_metadata = Gitlab::IssuableMetadata.new(current_user, models)