Use bulk INSERT to insert fixtures

Improves the performance from O(n) to O(1).
Previously it would require 50 queries to
insert 50 fixtures. Now it takes only one query.

Disabled on sqlite which doesn't support multiple inserts.

Fix current_page? helper issue with engine root path

Add test cases for optimistic locking

prepare for Minitest 6

Use of ParameterFilter no longer forces `request.filtered_parameters' class to be Hash

fix

fix

nodoc AC::Connection::WebSocket

Fix `Relation#exists?` queries with query cache

Prevent extra `scope` construction in `find_target`

Refactor #insert_fixtures to use Arel

Deprecate an `capify!` method in generators and templates

CI against JRuby 9.1.12.0

Fix examples for `AC::Parameters#to_query` [ci skip]

Without `permit`, `AC::Parameters#to_query` raise
`AC::UnfilteredParameters`.

```ruby
params = ActionController::Parameters.new({
  name: "David",
  nationality: "Danish"
})

params.to_query
# => ActionController::UnfilteredParameters: unable to convert unpermitted parameters to hash
```

http://jruby.org/2017/06/15/jruby-9-1-12-0.html

Add a test case for #28754

Remove debug print

Because constructing `scope` is a little expensive.

The `capify` command has been removed by Capistrano 3 and became to
`cap install`.
Therefore, the `capify!` method has no meaning in Capistrano 3.
I think that should deprecate.

Ref: https://github.com/capistrano/capistrano/commit/492793916acf32ffe1604daec6fd4892c8935018

This debug print was added in 87f5e5e2 for finding the regression caused
by d314646c and the regression has already been fixed in 969339bd.

A part for JSON was splitted from #28416 as #29273 and #29273 has
already been merged.

Closes #28754.
Closes #27588.

[Ryuta Kamizono & Bradley Priest]

Fixes FIXME: rb-inotify 0.99 has been released

[ci skip] Update fedora SQLite3 package name

Remove unused defined association

Remove FK together with column in MySQL

Unlike with other databses, MySQL doesn't let you remove the column
if there's a FK on this column.

For better developer experience we want to remove the FK together with
the column.

Raise on create for singular association when parent is unpersisted

Fix `create_table` with query from relation

Don't require 'unscope' to be the same on both sides of an 'or' relation

Use nullable `id` column instead of a primary key

Users should never publicly be interacting with an instance of this.  The instance that comes along with an `AC::Connection::Base` instance (the only thing a user should be working with) is [itself intended to be private](https://github.com/tjschuck/rails/blob/master/actioncable/lib/action_cable/connection/base.rb#L137-L140).

[ci skip]

Remove references to deprecared raise_runtime_errors from documentation, which is always enabled now. Ref: https://github.com/rails/sprockets-rails/commit/655b93bffc6f51b96a7cc097f9010942693bfaae and https://github.com/rails/rails/pull/24070 . Fixes #29483 [ci skip] (#29484)