chore: Use find_each instead of .all.each (#6975)

- Enable the rubocop Rails/FindEach
- Replace the .all.each with .find_each

This should let us avoid potential memory usage.
Motivation from the speedshop newsletter by Nate Berkopec

ref: https://www.rubyinrails.com/2017/11/16/use-find-each-instead-of-all-each-in-rails/
ref: https://linear.app/chatwoot/issue/CW-1480/chore-run-all-sidekiq-jobs-async

app/jobs/account/conversations_resolution_scheduler_job.rb

@@ -2,7 +2,7 @@ class Account::ConversationsResolutionSchedulerJob < ApplicationJob
   queue_as :scheduled_jobs
 
   def perform
-    Account.where.not(auto_resolve_duration: nil).all.each do |account|
+    Account.where.not(auto_resolve_duration: nil).all.find_each(batch_size: 100) do |account|
       Conversations::ResolutionJob.perform_later(account: account)
     end
   end

app/jobs/conversations/reopen_snoozed_conversations_job.rb

@@ -2,6 +2,6 @@ class Conversations::ReopenSnoozedConversationsJob < ApplicationJob
   queue_as :low
 
   def perform
-    Conversation.where(status: :snoozed).where(snoozed_until: 3.days.ago..Time.current).all.each(&:open!)
+    Conversation.where(status: :snoozed).where(snoozed_until: 3.days.ago..Time.current).all.find_each(batch_size: 100, &:open!)
   end
 end

app/jobs/inboxes/fetch_imap_email_inboxes_job.rb

@@ -2,7 +2,7 @@ class Inboxes::FetchImapEmailInboxesJob < ApplicationJob
   queue_as :low
 
   def perform
-    Inbox.where(channel_type: 'Channel::Email').all.each do |inbox|
+    Inbox.where(channel_type: 'Channel::Email').all.find_each(batch_size: 100) do |inbox|
       ::Inboxes::FetchImapEmailsJob.perform_later(inbox.channel) if inbox.channel.imap_enabled
     end
   end

app/jobs/migration/update_first_response_time_in_reporting_events_job.rb

@@ -6,7 +6,7 @@ class Migration::UpdateFirstResponseTimeInReportingEventsJob < ApplicationJob
 
   def perform(account)
     get_conversations_with_bot_handoffs(account)
-    account.reporting_events.where(name: 'first_response').each do |event|
+    account.reporting_events.where(name: 'first_response').find_each do |event|
       conversation = event.conversation
 
       # if the conversation has a bot handoff event, we don't need to update the response_time

app/jobs/trigger_scheduled_items_job.rb

@@ -3,7 +3,8 @@ class TriggerScheduledItemsJob < ApplicationJob
 
   def perform
     # trigger the scheduled campaign jobs
-    Campaign.where(campaign_type: :one_off, campaign_status: :active).where(scheduled_at: 3.days.ago..Time.current).all.each do |campaign|
+    Campaign.where(campaign_type: :one_off,
+                   campaign_status: :active).where(scheduled_at: 3.days.ago..Time.current).all.find_each(batch_size: 100) do |campaign|
       Campaigns::TriggerOneoffCampaignJob.perform_later(campaign)
     end