Fix a ContentNegotiation test description

Fix Time#advance to work with dates before 1001-03-07

Merge pull request #35663 from eileencodes/fix-database-configuration-when-not-actually-a-three-tier

Fix database configuration when adding another config level

This also prevents insert_all from leaking its attributes checks.

`values_list` is quite long and does far too many things. This also
eagerly extract the keys in initialize instead of having to worry about
calling them multiple times.

This is kind of hard to explain but if you have a database config with
another level like this:

```
development:
  primary:
    database: "my db"
    variables:
      statement_timeout: 1000
```

the database configurations code would chooke on the `variables` level
because it didn't know what to do with it.

We'd see the following error:

```
lib/active_record/database_configurations.rb:72:in
`block in find_db_config': undefined method `env_name' for [nil]:Array
(NoMethodError)
```

The problem here is that Rails does correctly identify this as not a
real configuration but returns `[nil]` along with the others. We need to
make sure to flatten the array and remove all the `nil`'s before
returning the `configurations` objects.

Fixes #35646

Internal usage for the method as public has removed at #29623.

[Alex Kitchens, Prathamesh Sonpatki]

In #10634 the behavior of Time#advance was changed to maintain a
proleptic gregorian calendar for dates before calendar reform. However
it didn't full address dates a long time before calendar reform and
they gradually drift away from the proleptic calendar the further you
go back in time. Fix this by always converting the date to gregorian
before calling advance which sets the reform date to -infinity.

 Revert "Pass HTML responses as plain-text in rails-ujs" 

Get rid of `Arel::Nodes::Values`

Closes #35159.

Fix invalid suggestion in null origin error message

That is completely covered by `Arel::Nodes::ValuesList`.

Related https://github.com/rails/arel/pull/484.

See discussion in #32287

This reverts commit 48e44edf.

See discussion in #32287

For HTML content in `ajax:success` handlers, `event.detail[0]` should
be an `HTMLDocument` instance.

Here is only place where we use `mb_chars` internally.

These are introduced after Rails 6.0.0 beta2.

[ci skip]

* Remove redundant `table_names.empty?`
* Early return in `truncate_tables` since it is already deeply nested
* Move `truncate_tables` out from between `exec_delete` and `exec_update`

https://buildkite.com/rails/rails/builds/59632#fe3d2551-569a-46c8-94f3-7abe835d4d7a/122-153

Before:

```
   (16.4ms)  TRUNCATE TABLE `author_addresses`
   (20.5ms)  TRUNCATE TABLE `authors`
   (19.4ms)  TRUNCATE TABLE `posts`
```

After:

```
  Truncate Tables (19.5ms)  TRUNCATE TABLE `author_addresses`;
TRUNCATE TABLE `authors`;
TRUNCATE TABLE `posts`
```

Add `-e/--environment` option to `rails initializers`

https://buildkite.com/rails/rails/builds/59622#924dff9d-85c2-4946-b264-a7e6ce01432c/122-130

This is to easier make `truncate_tables` to bulk statements.

Support Optimizer Hints

See #33912.

Raise UnknownAttributeError when unknown column is passed to insert_all and friends

We as Arm Treasure Data are using Optimizer Hints with a monkey patch
(https://gist.github.com/kamipo/4c8539f0ce4acf85075cf5a6b0d9712e),
especially in order to use `MAX_EXECUTION_TIME` (refer #31129).

Example:

```ruby
class Job < ApplicationRecord
  default_scope { optimizer_hints("MAX_EXECUTION_TIME(50000) NO_INDEX_MERGE(jobs)") }
end
```

Optimizer Hints is supported not only for MySQL but also for most
databases (PostgreSQL on RDS, Oracle, SQL Server, etc), it is really
helpful to turn heavy queries for large scale applications.

This allows specifying the environment as would any other rails commands.

Update docs for 'parameterize()' [ci skip]