If the argument is invalid, I think that it is more intuitive to use
`ArgumentError` than its own error class.

This fixes the following warnings:

```
rails/activejob/lib/active_job/test_helper.rb:119: warning: circular argument reference - except
rails/activejob/lib/active_job/test_helper.rb:166: warning: circular argument reference - except
```

This reverts commit 3420a145, reversing
changes made to afb66a5a.

* Allow a default value to be declared for class_attribute

* Convert to using class_attribute default rather than explicit setter

* Removed instance_accessor option by mistake

* False is a valid default value

* Documentation

fixed indentation.

rebased with master.

- removed predicate method. Used only reader.

".. with __dir__ we can restore order in the Universe." - by @fxn

Related to 5b8738c2

When define callbacks latest definition on the same callback/method
overwrites previous ones.

Active Job logging instrumentation is changed to log errors (with
backtrace) when a job raises an exception in #perform. This improves
debugging during development and test with the default configuration.

Prior to Rails 5, the default development configuration ran jobs with
InlineAdapter, which would raise exceptions to the caller and be
shown in the development log. In Rails 5, the default adapter was
changed to AsyncAdapter, which would silently swallow exceptions
and log a "Performed SomeJob from Async..." info message. This could
be confusing to a developer, as it would seem that the job was
performed successfully.

This patch removes the "Performed..." info message from the log
and adds an error-level "Error performing SomeJob..." log message
which includes the exception backtrace for jobs that raise an
exception within the #perform method. It provides this behavior for
all adapters.

Currently we provide the Job ID in logs only related to enqueuing a job.

This adds the job id to the remaining ActiveJob logs when:
 - a job started performing
 - a job ended performing

Providing the job id in those logs will ease searching logs by job id.

The `ActiveJob::TestHelper` replace the adapter to test adapter in
`before_setup`. It gets the target class using the `descendants`, but if
the test target job class is not loaded, will not be a replacement of
the adapter.
Therefore, instead of replacing with `before_setup`, modified to
replace when setting adapter.

Fixes #26360

Refactored ActiveJob TestAdapter

Updated ActiveJob changelog

Fixed typo in changelog

Fixed formatting issue in changelog

[ci skip]

`InlineAdapter` is not used from 1f8558fa.

Actually, private methods cannot be called with `self.`, so it's not just redundant, it's a bad habit in Ruby

This reverts commit 1e969bfb, reversing
changes made to a5041f26.

Reason: It breaks the public API

If we create nested (namespaced) rails engine such like bukkits-admin,
`bin/rails g scaffold User name:string age:integer`
will create
`bukkits-admin/app/controllers/bukkits/users_controller.rb`
but it should create
`bukkits-admin/app/controllers/bukkits/admin/users_controller.rb`.

In #6643, we changed `namespaced_path` as root path
because we supposed application_controller is always in root
but nested rails engine's application_controller will not.

Per https://www.timeanddate.com/counters/firstnewyear.html, it's already
2017 in a lot of places, so we should bump the Rails license years to
2017.

[ci skip]

This removes the following warnings.

```
/home/travis/build/rails/rails/activejob/lib/active_job/test_helper.rb:241: warning: shadowing outer local variable - job
/home/travis/build/rails/rails/activejob/lib/active_job/test_helper.rb:265: warning: shadowing outer local variable - job
```

https://bugs.ruby-lang.org/issues/12739