Follow up of #19171 and #26825.

Add math test

After #449 was merged math can be done on these
nodes, adding a test file to unit test all the
math operators.

Don't generate `config/spring.rb` in `app:update` task when spring isn't loaded

Add available transformations to docs

`foreign_key`, `json` and `virtual` are also available.

Follow up of #32605.

Remove ActiveRecord::Transactions#rollback_active_record_state!

Don't clear transaction state after manual rollback

`rollback_active_record_state!` was removed from `save!` but not `save`
in da840d13. I believe that leaving it
in `save` was a mistake, since that commit was intended to move the
rollback logic from the `save`/`save!` call to the transaction stack.

As of 67d8bb96 the record's original
state is lazily restored the first time it's accessed after the
transaction, instead of when a rollback occurs. This means that the call
to `restore_transaction_record_state` here has no effect: the record's
transaction level is incremented twice (in rollback_active_record_state!
and `with_transaction_returning_status`), isn't decremented again until
the the `ensure` block runs, and won't hit zero until the next time
`sync_with_transaction_state` is called.

I'm not sure what originally wanted to pass to the argument.
However, as long as see the document added along with the commit, it seems just
to be mistaken that trying to pass the error instance.
https://github.com/rails/rails/pull/30622/files#diff-59beb0189c8c6bc862edf7fdb84ff5a7R64

Fixes #32853

Remove unused `remove_file` method

Remove reference to old `:text` rendering option

[ci skip]

`becomes` creates new object and copies attributes from the receiver. If
new object has mutation tracker which is created in `after_initialize`,
it should be cleared since it is for discarded attributes.

But if the receiver doesn't have mutation tracker yet, it will not be
cleared properly.

It should be cleared regardless of whether the receiver has mutation
tracker or not.

Fixes #32867.

Added a lot of Oxford commas

[ci skip] A regular expression was used to find a lot of missing Oxford
commas and add them.  The regular expression was as follows.

", ([a-zA-Z0-9.\`:'\"]+ ){1,6}(or|and) "

Fix Typo In ActiveSupport Instrumentation Guide

If an `ActiveRecord::Rollback` error was raised by a persistence method
(e.g. in an `after_save` callback), this logic would potentially discard
the original state of the record from before the transaction, preventing
it from being restored later when the transaction was rolled back.

Fix ActiveRecord::AttributeMethods::Dirty documentation

Add option to ActiveStorage::Blob to set extract_content_type_from_io

This adds a boolean argument called identify to ActiveStorage::Blob
methods #create_after_upload, #build_after_upload and #upload. It
allows a user to bypass the automatic content_type inference from
the io.

In #32780, We have supported the `--skip-sprockets` option in the `app:update` task.
When `options[:api]` is truthy, `option[:skip_sprockets]` is also truthy. So we can remove this `remove_file` method.
https://github.com/rails/rails/blob/42b9e7e50c084e119a679cf155b70b5efc4d36ff/railties/lib/rails/generators/rails/app/app_generator.rb#L281-L283

The prefix of `new` and `edit` generated by `resources` is singular.

Remove leftover requires

* Concurrent::Map usage was removed from this file in 3239ed48

* Monitor usage was removed in f233598d

Fix output in routing.md [ci skip]

Previously the documentation for the newly introduced (in 5.1) AR::Dirty
methods was misleading, as it stated the the new methods were aliases
for the old methods. This was false, and caused confusion when the
differences in their implementation became apparent.

This change attempts to describe the behaviour of these methods more
accurately, also noting when they are likely to be useful (i.e. before
or after saving a record).

This change also makes minor updates to consistently format the
documentation of this API, in accordance with the API Documentation
Guidelines.

Follow up of #32034.

Once all technicalities have been introduced, the purpose of this
paragraph is to precisely unroll expressions like "the String class".
That way, the reader is forced to clearly separate concepts that Ruby
programmers often have kind of blurred:

  * Constants are storage, like variables.

  * Ruby does not have syntax for class or module names.

  * `String` is a regular constant that holds a value. In this case, the
    value happens to be a class object.

  * Constants are stored in class and module objects. In the case of
    `String`, the holder is the class object stored in the `Object`
    constant.

Understanding that paragraph the way is written is important to
accomplish this objective.

References #32818.

Active Record postgresql documentation for bit string types corrected [ci skip]

https://travis-ci.org/rails/rails/jobs/375326992#L1160-L1166

I saw these ones while working on #32362.

File.write was introduced in Ruby 1.9.3 and it is the most concise way
to perform bulk writes (as File.read is for bulk reading).

The existing flags enabled binmode, but we are dumping text here.
The portable way to dump text is text mode. The only difference is
newlines, and portable code should in particular emit portable newlines.

Please note the hard-coded \ns are still correct. In languages with C
semantics for newlines like Ruby, Python, Perl, and others, "\n" is a
portable newline. Both when writing and when reading. On Windows, the
I/O layer is responsible for prepending a CR before each LF on writing,
and removing CRs followed by LFs on reading. On Unix, binmode is a
no-op.

Don't generate assets' initializer in `app:update` task if sprockets is skipped

Execute `rails new myapp -S` and then upgrade the app by using the `app:update` task, `bin/rails c` results in `NoMethodError`.

```
$ bin/rails app:update

$ bin/rails c
Traceback (most recent call last):
    44: from bin/rails:4:in `<main>'
(snip)
     1: from /Users/tanimichi.tsukuru/ghq/github.com/moneyforward/moneyplus/config/initializers/assets.rb:4:in `<top (required)>'
/Users/tanimichi.tsukuru/ghq/github.com/moneyforward/moneyplus/vendor/bundle/ruby/2.5.0/gems/railties-5.2.0/lib/rails/railtie/configuration.rb:97:in `method_missing': undefined method `assets' for #<Rails::Application::Configuration:0x00007fcb8d3697e0> (NoMethodError)
Did you mean?  asset_host
```