[Perf] Don't use Enumerable#next in pluck since it is very slow

Using indent method to refactor controller generator.

[John J. Wang & Prathamesh Sonpatki]

[Performance] Don't create fibers while merging bind variables

FIX reload! within rails console --sandbox causes undefined method rollb...

FIX reload! within rails console --sandbox causes undefined method rollback upon exiting [https://github.com/rails/rails/issues/11834]

Fix typo in generators test helpr -> helper [ci skip]

Fix broken link to Fixtures documentation on guides and activerecord tests [ci skip]

and activerecord tests

[ci skip]

Port all remaining self.protected_instance_variables to class methods

ActiveRecord: Include usecs when quoting DateTime in PostgreSQL adapter

* typecast:
  correctly typecast keys, remove conditionals, reduce object allocations
  no need to to_a the scope
  remove extra flat_map array
  avoid extra empty array allocation
  extract owner id calculation to a method
  only call to_a when we have to