We are moving to using `DatabaseConfig` objects everywhere inside of
Rails instead of passing around Hash objects.

This PR moves to using `DatabaseConfig` objects inside of the individual
database tasks adapters. In the interest of not breaking existing
adapters, we've introduced an upgrade path by which adapters can get a
hold of database configuration objects instead of Hashes by implementing
a method `self.using_database_configurations?`
Co-authored-by: Neileencodes <eileencodes@gmail.com>

Update test to avoid Puma output format change

We are seeing some test failures for this test in #37291. It looks like
what's going on is that Puma has changed the output for this command
between 4.1 and 4.2

Previously:

```
...
* Environment: development
* Listening on tcp://localhost:3000
...

```

Now:

```
...
* Environment: development
* Listening on tcp://127.0.0.1:3000
* Listening on tcp://[::1]:3000
...

```

So to get around this, instead of checking the binding address, just
check for the presence of 'Listening' generally like we do on server
start.
Co-authored-by: Neileencodes <eileencodes@gmail.com>

Fix typo, shoud -> should [ci skip]

Since the original message is something like this

    expected file ... to define constant A, but didn't

the \S+ captured the comma. A constant name goes there, so [\w:]+ is
enough and won't match the comma.

Better double checked locking in load_schema

Allow setting a different log level per request.

Instantiate ConnectionPool with a DatabaseConfig rather than a ConnectionSpecification

Fixed typo in comment in ActionCable::Connection::TestCase [ci skip]

Make all reads on configuration_hash use methods

This may happen in engines loaded as gems, for example.

Closes #37285.

Using `self` works by essentially pointing to the included class, in
this case `ActiveJob::Base`, so that'd end up delegating to
`ActiveJob::Base.queue_adapter` instead.

Follow up #37281.

Fix typo in actionpack changelog, `a HTTP` -> `an HTTP` [ci skip]

Convert all uses of `db_config.configuration_hash[*]` to use methods
defined on an implementation of `DatabaseConfigurations::DatabaseConfig`.

Since we want to get away from accessing properties directly on the
underlying configuration hash, we'll move here to accessing those values
via the implementations on `DatabaseConfig` (or more specifically,
`HashConfig`).

There are still codepaths that are passing around `configuration_hash`,
and follow-on PRs will address those with the goal of using
configuration objects everywhere up until the point we pass a resolved
hash over to the underlying client.
Co-authored-by: Neileencodes <eileencodes@gmail.com>

Make UrlConfig a subclass of HashConfig

A `UrlConfig` is a `HashConfig` that mixes in connection information
based on a `url` passed from the constructor.

Previously, for each new property we wanted to introduce an accessor
for, we'd need to write an implementation for `HashConfig` _and_ for
`UrlConfig`.

Now we make `UrlConfig` descend from `HashConfig` so we can write a
single implementation for both cases.

Also while we're in here, take the `adapter` implementation into
`HashConfig` so that `DatabaseConfig` isn't making any assumptions about
the structure of its subclasses.
Co-authored-by: Neileencodes <eileencodes@gmail.com>

Remove UrlConfig#url_config?

Resolve Hash with `url` key as a `UrlConfig`

This private method is only used in one place, to check whether an
object we have is an instance of `UrlConfig`.

Instead we can just check that we have the right type of object

In `DatabaseConfigurations#configs_for`, `Hash` configs that contain a
`:url` key resolve to a `UrlConfig`.  Since we weren't mirroring that behavior
in `Resolver`, we had to add explicit handling for `url` keys to the
`HashConfig` implementation.

Now we're going to always resolve these hashes as `UrlConfig` and can
remove the extra implementation of URL handling from `HashConfig`.

Of course, this does introduce some duplication between
`DatabaseConfigurations` and `Resolver` which we plan to address in a
future PR.
Co-authored-by: Neileencodes <eileencodes@gmail.com>