Add rails:update to the upgrading guides

[ci skip]
Add warning for `rescue_from Exception` and `rescue_from StandardError`

[ci skip]
Replace x.sort_by!.select! with x.select!.sort_by!

The latter has the same speed as the former in the worst case
and faster in general, because it is always better to sort less items.

Unfortunately, `routes.select!{...}.sort_by!{...}` is not possible here
because `select!` returns `nil`, so select! and sort! must be done
in two steps.
Delegate #model_name method to self.class
remove unnecessary require for json serialization test cases
Merge pull request #15882 from aditya-kapoor/remove-unnecessary-require

remove unnecessary require from json serialization test cases
Remove unused param 'klass' from AttributeAssignment#read_other
Remove unused param 'conn' from ConnectionPool#release
Disable autolink in example code blocks in guides.

/cc @chancancode @robin850

configuration reference: http://alexgorbatchev.com/SyntaxHighlighter/manual/configuration/

Related issues:

* https://github.com/vmg/redcarpet/issues/334

* https://github.com/docrails-tw/guides/issues/62
Merge pull request #15886 from JuanitoFatas/disable-autolink

Disable autolink in example code blocks in guides. [ci skip]
Merge pull request #15881 from mmozuras/remove_unused_params

Remove unused params
Merge pull request #15810 from maurogeorge/guides-rails-update

Add rails:update to the upgrading guides
add missing `:nodoc:` for recent refactorings. [ci skip]

Adding `# :nodoc:` to the parent `class` / `module` is not going
to ignore nested classes or modules.

There is a modifier `# :nodoc: all` but sadly the containing class
or module will continue to be in the docs.

/cc @sgrif
Merge pull request #15871 from yuki24/add-model-name-instance-method

Add #model_name instance method to ActiveModel::Naming
add missing `:nodoc:` to `store.rb`. [ci skip]
`:nodoc: all` does not remove the constants from the API. [ci skip]

Need to add individual `:nodoc:` for nested classes / modules to completely
remove the constants from the API.
Silence warning in test

We still had one file using `column_for_attribute` when it could return
nil, causing deprecation warnings in the tests.
Merge pull request #15894 from sgrif/sg-silence-warning-in-test

Silence warning in test
Always assume strings with non-numeric characters change numeric types

We previously only did this if the old value was zero, to make sure
numericality validations run and failed if the user gave 'wibble' as the
value, which would be type cast to 0. However, numericality validations
will fail if there are any non-numeric characters in the string, so 5 ->
'5wibble' should also be marked as changed.
Merge pull request #15895 from sgrif/sg-numeric-changes

Always assume strings with non-numeric characters change numeric types