Define the Duration#instance_of? method

Since Duration is extending from ProxyObject which extends itself from
BasicObject, the Duration object doesn't respond to the #instance_of?
method. Thus, the #method_missing hook get triggered, delegating the
method to its `value` attribute.

However, Rubinius' #eql? definition relies on #instance_of?, thus this
will equal to true with a Fixnum (since its `value` attribute is a
Fixnum) while it should not.

The previous behavior was wrong anyway, no matter the implementation.
Added enqueue_at support for QueAdapter in ActiveJob

* Added inline job runner for Que in test/support
* Updated QueAdapter to support enqueue_at
adding the exception RecordNotFound to UUID find
Don't fight against ourselves for the default log level

If we want to always default to :debug, let's just do that.

At which point the production.rb entry can become an "uncomment to
change" instead.
Refactor ActionDispatch::RemoteIp

Refactored IP address checking in ActionDispatch::RemoteIp to rely on
the IPAddr class instead of the unwieldly regular expression to match
IP addresses. This commit keeps the same api but allows users to pass
IPAddr objects to config.action_dispatch.trusted_proxies in addition
to passing strings and regular expressions.

Example:

    # config/environments/production.rb
    config.action_dispatch.trusted_proxies = IPAddr.new('4.8.15.0/16')
Replacing an each with reduce

The functionality has not changed, but the code is more elegant by
using `reduce` instead of `each`.

This way no accumulator needs to be declared, no explicit return is
needed.
fix server names [ci skip]

Per feedback in https://github.com/rails/rails/commit/af63e4a2546629c3fb2d53cffb7d4ea0e8663f68#commitcomment-7477636
fix grammar [ci skip]
Merge pull request #16604 from saarons/clean-remote-ip-middleware

ActionDispatch::RemoteIp accept IPAddr matches for trusted proxies
Revert "Add I18n support for `:placeholder` HTML option is passed to form fields"
Merge pull request #16629 from rails/revert-16438-input-placeholder-i18n

Revert "Add I18n support for `:placeholder` HTML option is passed to for...
[ci skip] Added documentation for has_and_belongs_to_many scope parameter
Merge pull request #16630 from tomkadwill/added_has_and_belongs_to_many_scope_documentation

[ci skip] Added documentation for has_and_belongs_to_many scope parameter
[ci skip] Running AR tests guide [Fixes GH-15891]

Patch by @bcjordan
Follow up on #16408

[skip ci]
Merge branch 'jonatack-patch-8'
add nested_model_forms to guides/documents.yaml [wip] [ci skip]
Merge pull request #11859 from zzak/nested_model_forms_guide

See AR::Associations for greater detail in Nested Model Forms Guide [ci skip]
Pass logging message through block.

This follows the good practice listed on http://guides.rubyonrails.org/debugging_rails_applications.html#impact-of-logs-on-performance
Missing space. [CI SKIP]