Load test fixtures where data are needed

Without this, some tests here were not actually testing anything.
Avoid sorting an Array including objects from different Classes

addresses "ArgumentError: comparison of VerySpecialComment with SpecialComment failed" in ActiveRecord::DelegationRelationTest#test_#sort!_delegation_is_deprecated
tidy Active Record CHANGELOG. [ci skip].
Fixed typo in migrations guide

Product model name was pluralized in example in migrations guide.
[ci skip]
Merge pull request #12847 from jipe/master

Fixed typo in migrations guide [ci skip]
Do not count "SHOW CREATE TABLE" queries when testing against mysql
Explicitly exit with status "1" for create and drop failures

* A non-zero exit status allows subsequent shell commands to be chained
  together such as: `rake db:reset test:prepare && rspec && cap deploy`
  (if you're feeling brave :)
* Any exceptions raised during the `create` and `drop` tasks are caught
  in order to print a "pretty" message to the user. Unfortunately doing
  so prevents rake from aborting with a non-zero exit status to the shell.
* Therefore we re-raise the exceptions after the "pretty" message and
  re-catch them in the task.
* From the task we explicitly exit with a non-zero status. This method
  was chosen (rather than just letting rake fail from the exception) so
  that the backtrace is suppressed and the output to stderr is
  unchanged.
* Update activerecord CHANGELOG
test cases to describe the MySQL boolean behavior.
Unifies mysql and mysql2 casting of booleans.
Merge pull request #12425 from senny/mysql_booleans

Unify boolean quoting for Mysql- and Mysql2Adapter.
Merge pull request #12815 from Adam89/patch-1

Update security.md [ci skip]
Prevent the counter cache from being decremented twice

when destroying a record on a has_many :through association.
:destroy method has own counter_cache callbacks.
documentation updated for Hashes [ci skip]
Merge pull request #12748 from dm1try/fix_counter_cache_for_through_association

Fixes #11079, prevent the counter cache from being decremented twice when destroying a record on a has_many :through association
Merge pull request #12854 from kuldeepaggarwal/f-indentation

methods and outputs indented [ci skip]
updated documentation for Integer
Allow Pathnames to be added to eager load paths
Make static error pages responsive
Merge pull request #12555 from EtienneLem/responsive-static-pages

Make static error pages responsive
Change syntax format for example returned values

According to our guideline, we leave 1 space between `#` and `=>`, so we
want `# =>` instead of `#=>`.

Thanks to @fxn for the suggestion.

[ci skip]