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Merge pull request #10710 from senny/5554_let_the_database_raise_on_counts

Remove column restrictions for `#count`, let the database raise if the SQL is invalid.
Refactored ActiveRecord `first` method to get rid of duplication.
Don't blindly call blame_file! on exceptions in ActiveSupport::Dependencies::Loadable

It is possible under some environments to receive an Exception that is
not extended with Blamable (e.g. JRuby).
ActiveSupport::Dependencies::Loadable#load_dependency blindly call
blame_file! on the exception which throws it's own NoMethodError
exception and hides the original Exception.

This commit fixes #9521
Merge pull request #10795 from atambo/master

Don't blindly call blame_file! on exceptions in ActiveSupport::Dependes::Loadable
fix ActiveModel::Validations.validators_on doc
Merge pull request #10906 from darai2k/fix-activemodel-validations-doc

fix ActiveModel::Validations.validators_on doc
Merge pull request #10897 from prathamesh-sonpatki/active-support-typos

Fixed typos in activesupport [ci skip]
rename method `find_first_records` to `find_first_with_limit`
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.
Calls to the application constant have been refactored to use
Rails.application when drawing routes and creating other configurations
on the application.
remove some evals from callback conditionals
reduce evals in depdendent associations
remove evals from the association
indentation
adding callbacks should be private
remove evaled belongs_to counter cache method
push before_destroy counter cache method to a single method
push belongs_to counter cache method to a single method
use attribute methods for finding key values rather than generating method names