that complements the `start`parameter to specify where to stop batch processing

[ci skip]

Closes #16538

This patch removes the tasks doc:app, doc:rails, and doc:guides.

In our experience applications do not generate APIs using doc:app.
Methods may be certainly documented for maintainers, annotated
with YARD tags, etc. but that is intended to be read with the
source code, not in a separate website. Then, teams also have
typically selected topics written down in Markdown files, or in
a GitHub wiki... that kind of thing.

If a team absolutely needs to generate application documentation
for internal purposes, they can still easily write their own task.

Regarding doc:rails and doc:guides, we live in 2015. We are used
to go to online docs all the time. If you really want access to the
API offline RubyGems generates it for every Rails component unless
you tell it not to, and you can checkout the Rails source code to
read the guides as Markdown, or download them for a Kindle reader.

All in all, maintaining this code does not seem to be worthwhile
anymore.

As a consequence of this, guides (+3 MB uncompressed) won't be
distributed with the rails gem anymore. Of course, guides and API
are going to be still part of releases, since documentation is
maintained alongside code and tests.

Also, time permitting, this will allow us to experiment with novel
ways to generate documentation in the Rails docs server, since
right now we were constrained by being able to generate them in
the user's environment.

improve sentence flow with grammar change

in `ActionController::TestCase` and
`ActionDispatch::Integration`

Old syntax:

    `xhr :get, :create, params: { id: 1 }`

New syntax example:

    `get :create, params: { id: 1 }, xhr: true`

ref https://bugs.ruby-lang.org/issues/8846

New wording is based on the "cref" sentence earlier in the section.

[ci skip]

Non-kwargs requests are deprecated now.
Guides are updated as well.

`post url, nil, nil, { a: 'b' }` doesn't make sense.
`post url, params: { y: x }, session: { a: 'b' }` would be an explicit way to do the same

The default command prompt under Windows doesn't run binstubs correctly
while PowerShell needs to find the location of the Ruby interpreter for
it to work properly. Passing the binstubs manually to the interpreter
solves this problem.

To be able to return type of validator, one can now call `details`
on Errors instance:

```ruby
class User < ActiveRecord::Base
  validates :name, presence: true
end
```

```ruby
user = User.new; user.valid?; user.errors.details
=> {name: [{error: :blank}]}
```

Move a introduction of `Module.nesting` to the beginning of sentence.
This change will help reader to try to dump `nesting`.

Change all of anchor text in the nav links to `Back` and `Edit`
Use `Edit | Back` on pages that use both links to conform to what
scaffolding generates.

Use consistent anchor text throughout the guide.

Change all of anchor text in the nav links to `Back` and `Edit`
Use `Edit | Back` on pages that use both links to conform to what
scaffolding generates.

Reference #18533

 - Followup of https://github.com/rails/rails/pull/18503.

- Changed `IN` to `ON` in all note sentences in guides.