Merge pull request #16379 from JackDanger/update-preloader-documentation

Updating Associations::Preloader docs
ActiveJob Integration Tests
MySQL: correct LONGTEXT and LONGBLOB limits from 2GB to their true 4GB
MySQL: schema.rb now includes TEXT and BLOB column limits.
Include default column limits in schema.rb

Allows :limit defaults to be changed without pulling the rug out from
under old migrations that omitted :limit because it matched the default
at the time.
Speed up schema dumper tests

Dump the standard schema once instead of redoing it per test
Merge pull request #16541 from cristianbica/activejob-integration-tests

ActiveJob Integration Tests
Merge pull request #16839 from chancancode/default_test_order

Default to sorting user's test cases for now
Fix typo
Set the test order to be random in the generated app

This will avoid the warning in our tests. We delete all the
config/environments/ files in the test app so our default code will not
work.
Set test order in ActiveSupport::TestCase of isolation/abstract_unit
Define the configuration at Active Support
Always define capture to remove the deprecation message
Changed the DangerousAttributeError exception message to include messaging that the conflict could be because of a conflicting attribute.
A `NullRelation` should represent nothing. Closes #15176.

[Matthew Draper & Yves Senn]

Closes #16860. (pull request to discuss the implementation)
switch `assert_operator` arguments as discussed in #16860.

Working with two different machines is hard :sweat:
Explain ERB space removal. [ci skip]
Changes puts to logger.info
Merge pull request #16874 from Bartuz/patch-1

[docs] Changes puts to logger.info [ci skip]
reuse view test-cases for pg materialized view tests.