DEV: Don't user before(:all)/after(:all) (#13389)

Leaking state and non-obvious order (before :all runs *before* RailsHelper.test_setup) are not worth it.
A replacement PR for #13370. Fixes some flaky specs, e.g.
```
bin/rspec './spec/components/freedom_patches/translate_accelerator_spec.rb[1:3]' './spec/jobs/clean_up_user_export_topics_spec.rb[1:1]' --tag ~type:multisite --seed 35994
```

Also included:
* DEV: No need for locale reset (we do it anyway in rails_helper in `test_setup`)

spec/lib/backup_restore/local_backup_store_spec.rb

@@ -5,19 +5,16 @@ require 'backup_restore/local_backup_store'
 require_relative 'shared_examples_for_backup_store'
 
 describe BackupRestore::LocalBackupStore do
-  before(:all) do
+  before do
     @root_directory = Dir.mktmpdir
     @paths = []
-  end
-
-  after(:all) do
-    FileUtils.remove_dir(@root_directory, true)
-  end
-
-  before do
     SiteSetting.backup_location = BackupLocationSiteSetting::LOCAL
   end
 
+  after do
+    FileUtils.remove_dir(@root_directory, true)
+  end
+
   subject(:store) { BackupRestore::BackupStore.create(root_directory: @root_directory) }
   let(:expected_type) { BackupRestore::LocalBackupStore }
 

spec/lib/backup_restore/s3_backup_store_spec.rb

@@ -6,7 +6,7 @@ require 'backup_restore/s3_backup_store'
 require_relative 'shared_examples_for_backup_store'
 
 describe BackupRestore::S3BackupStore do
-  before(:all) do
+  before do
     @s3_client = Aws::S3::Client.new(stub_responses: true)
     @s3_options = { client: @s3_client }
 
@@ -65,9 +65,7 @@ describe BackupRestore::S3BackupStore do
         last_modified: Time.zone.now
       }
     end)
-  end
 
-  before do
     SiteSetting.s3_backup_bucket = "s3-backup-bucket"
     SiteSetting.s3_access_key_id = "s3-access-key-id"
     SiteSetting.s3_secret_access_key = "s3-secret-access-key"
@@ -82,7 +80,7 @@ describe BackupRestore::S3BackupStore do
 
   context "S3 specific behavior" do
     before { create_backups }
-    after(:all) { remove_backups }
+    after { remove_backups }
 
     describe "#delete_old" do
       it "doesn't delete files when cleanup is disabled" do

spec/lib/backup_restore/shared_examples_for_backup_store.rb

@@ -2,7 +2,7 @@
 
 shared_context "backups" do
   before { create_backups }
-  after(:all) { remove_backups }
+  after { remove_backups }
 
   # default backup files
   let(:backup1) { BackupFile.new(filename: "b.tar.gz", size: 17, last_modified: Time.parse("2018-09-13T15:10:00Z")) }