When we un-escape HTML text to find references in it, we should then
re-escape the whole text again, not only found matches.

Because we replace matches with milestone/label links (which contain
HTML tags we don't want to escape again), we re-escape HTML text
with placeholders instead of these links and then replace placeholders
in the escaped text.

Add frozen_string_literal to spec/support

See merge request gitlab-org/gitlab-ce!31132

Using the sed script from
https://gitlab.com/gitlab-org/gitlab-ce/issues/59758

This makes these tests available for other implementations

Avoid doing sequential database queries to load the namespaces and the
routes of projects and namespaces.

This results in the following query:

```sql
SELECT "projects"."id" AS t0_r0,
       "projects"."name" AS t0_r1,
       "projects"."path" AS t0_r2,
       "projects"."description" AS t0_r3,
       "projects"."created_at" AS t0_r4,
       "projects"."updated_at" AS t0_r5,
       "projects"."creator_id" AS t0_r6,
       "projects"."namespace_id" AS t0_r7,
       "projects"."last_activity_at" AS t0_r8,
       "projects"."import_url" AS t0_r9,
       "projects"."visibility_level" AS t0_r10,
       "projects"."archived" AS t0_r11,
       "projects"."avatar" AS t0_r12,
       "projects"."import_status" AS t0_r13,
       "projects"."star_count" AS t0_r14,
       "projects"."import_type" AS t0_r15,
       "projects"."import_source" AS t0_r16,
       "projects"."import_error" AS t0_r17,
       "projects"."ci_id" AS t0_r18,
       "projects"."shared_runners_enabled" AS t0_r19,
       "projects"."runners_token" AS t0_r20,
       "projects"."build_coverage_regex" AS t0_r21,
       "projects"."build_allow_git_fetch" AS t0_r22,
       "projects"."build_timeout" AS t0_r23,
       "projects"."pending_delete" AS t0_r24,
       "projects"."public_builds" AS t0_r25,
       "projects"."last_repository_check_failed" AS t0_r26,
       "projects"."last_repository_check_at" AS t0_r27,
       "projects"."container_registry_enabled" AS t0_r28,
       "projects"."only_allow_merge_if_pipeline_succeeds" AS t0_r29,
       "projects"."has_external_issue_tracker" AS t0_r30,
       "projects"."repository_storage" AS t0_r31,
       "projects"."request_access_enabled" AS t0_r32,
       "projects"."has_external_wiki" AS t0_r33,
       "projects"."ci_config_path" AS t0_r34,
       "projects"."lfs_enabled" AS t0_r35,
       "projects"."description_html" AS t0_r36,
       "projects"."only_allow_merge_if_all_discussions_are_resolved" AS t0_r37,
       "projects"."printing_merge_request_link_enabled" AS t0_r38,
       "projects"."auto_cancel_pending_pipelines" AS t0_r39,
       "projects"."import_jid" AS t0_r40,
       "projects"."cached_markdown_version" AS t0_r41,
       "projects"."delete_error" AS t0_r42,
       "projects"."last_repository_updated_at" AS t0_r43,
       "projects"."storage_version" AS t0_r44,
       "projects"."resolve_outdated_diff_discussions" AS t0_r45,
       "projects"."repository_read_only" AS t0_r46,
       "projects"."merge_requests_ff_only_enabled" AS t0_r47,
       "projects"."merge_requests_rebase_enabled" AS t0_r48,
       "projects"."jobs_cache_index" AS t0_r49,
       "projects"."pages_https_only" AS t0_r50,
       "projects"."remote_mirror_available_overridden" AS t0_r51,
       "projects"."pool_repository_id" AS t0_r52,
       "projects"."runners_token_encrypted" AS t0_r53,
       "projects"."bfg_object_map" AS t0_r54,
       "namespaces"."id" AS t1_r0,
       "namespaces"."name" AS t1_r1,
       "namespaces"."path" AS t1_r2,
       "namespaces"."owner_id" AS t1_r3,
       "namespaces"."created_at" AS t1_r4,
       "namespaces"."updated_at" AS t1_r5,
       "namespaces"."type" AS t1_r6,
       "namespaces"."description" AS t1_r7,
       "namespaces"."avatar" AS t1_r8,
       "namespaces"."share_with_group_lock" AS t1_r9,
       "namespaces"."visibility_level" AS t1_r10,
       "namespaces"."request_access_enabled" AS t1_r11,
       "namespaces"."description_html" AS t1_r12,
       "namespaces"."lfs_enabled" AS t1_r13,
       "namespaces"."parent_id" AS t1_r14,
       "namespaces"."require_two_factor_authentication" AS t1_r15,
       "namespaces"."two_factor_grace_period" AS t1_r16,
       "namespaces"."cached_markdown_version" AS t1_r17,
       "namespaces"."runners_token" AS t1_r18,
       "namespaces"."runners_token_encrypted" AS t1_r19,
       "routes"."id" AS t2_r0,
       "routes"."source_id" AS t2_r1,
       "routes"."source_type" AS t2_r2,
       "routes"."path" AS t2_r3,
       "routes"."created_at" AS t2_r4,
       "routes"."updated_at" AS t2_r5,
       "routes"."name" AS t2_r6,
       "routes_projects"."id" AS t3_r0,
       "routes_projects"."source_id" AS t3_r1,
       "routes_projects"."source_type" AS t3_r2,
       "routes_projects"."path" AS t3_r3,
       "routes_projects"."created_at" AS t3_r4,
       "routes_projects"."updated_at" AS t3_r5,
       "routes_projects"."name" AS t3_r6
FROM "projects"
LEFT OUTER JOIN "namespaces" ON "namespaces"."id" = "projects"."namespace_id"
LEFT OUTER JOIN "routes" ON "routes"."source_id" = "namespaces"."id"
AND "routes"."source_type" = $1
LEFT OUTER JOIN "routes" "routes_projects" ON "routes_projects"."source_id" = "projects"."id"
AND "routes_projects"."source_type" = $2
LEFT OUTER JOIN "project_repositories" ON "projects"."id" = "project_repositories"."project_id"
WHERE ("projects"."storage_version" IS NULL
       OR "projects"."storage_version" = 0)
  AND "project_repositories"."project_id" IS NULL
  AND ("projects"."id" BETWEEN $3 AND $4);
  -- [["source_type", "Namespace"],
  --  ["source_type", "Project"],
  --  ["id", 1],
  --  ["id", 4]]
```