Use symbols instead of strings

ActiveSupport::Concern is used all over Rails
This PR will only create 3 new objects as keys are never recreated and
are not subject to garbage collection.

The strings were being uniquely created and garbage collected. I don't
have any performance numbers but this should be better than all of the
GC.
Making the rake file for tests easier to read.

I'm defining a new class which modularizes how the `rake test` tasks are
defined and invoked.
Improved grammar and replaced 'dbs' slang with 'databases'
Removed support for deprecated `counter_sql`
Merge pull request #11241 from neerajdotname/deprecated-counter-sql

Removed support for deprecated `counter_sql`
Add CHANGELOG enty for #11235
Removed support for deprecated `finder_sql` in associations.
fix indentation
use extract_options!
Merge pull request #11251 from neerajdotname/deprecated-finder-sql

Removed support for deprecated finder sql
Merge pull request #11252 from neerajdotname/use-extract-options

use extract_options!
Removed support for deprecated `insert_sql` in associations.
Merge pull request #11253 from neerajdotname/removed-insert-sql

Removed support for deprecated `insert_sql` in associations.
resolve aliases before passing the hash to the predicate builder
no need to to_sym the column name, leave it as-is
Removed support for deprecated `delete_sql` in associations.
Merge pull request #11254 from neerajdotname/delete-sql-be-gone

Removed support for deprecated `delete_sql` in associations.
Dropped deprecated option `:restrict` for `:dependent` in associations
Merge pull request #11255 from neerajdotname/restrict-be-gone

Dropped deprecated option `:restrict` for `:dependent` in associations
deprecated `ActiveRecord::TestCase` is no longer public.

/cc @tenderlove