avoid using alias in generators

Ruby's alias produces public methods, causing a spurious Thor task
to be created.  For example, this is the reason MigrationGenerator
currently has two tasks:

    > ActiveRecord::Generators::MigrationGenerator.all_tasks.keys
    => ["singular_name", "create_migration_file"]

singular_name was meant to be an attribute, not a task.  Because it's
public, it gets called as a task every time the generator is invoked.

The fix is to ensure all generator methods have the correct
visibility.
Hash#deep_*_keys(!) recurse into nested arrays.

Following methods now recursively transform nested arrays, too.

* Hash#deep_transform_keys
* Hash#deep_transform_keys!
* Hash#deep_stringify_keys
* Hash#deep_stringify_keys!
* Hash#deep_symbolize_keys
* Hash#deep_symbolize_keys!
Check authentication scheme in Basic auth

`authenticate_with_http_basic` and its families should check the authentication
schema is "Basic".

Different schema, such as OAuth2 Bearer should be rejected by basic auth, but
it was passing as the test shows.

This fixes #10257.
Run login_procedure only when the auth_scheme is valid
Fix serialized field returning serialized data after update_column
Fixes Issue #13466.

Changed the call to a scope block to be evaluated with instance_eval.
The result is that ScopeRegistry can use the actual class instead of base_class when
caching scopes so queries made by classes with a common ancestor won't leak scopes.
Fixed a problem where `sum`, `size`, `average`, `minimum` and `maximum` used
with a grouping was not returning a Hash.
Put attr_reader in with all of the other instance methods

This makes the grouping make a little more sense
Distinguish rake assets:clobber from rake assets:clean
Fix confusing exception in ActiveSupport delegation
Have Postgres OID types inherit from general types

Using general types where possible. Several more can go away once
infinity gets figured out.
Replace `type_cast` case statement with delegation

All subclasses of column were now delegating `type_cast` to their
injected type object. We can remove the overriding methods, and
generalize it on the `Column` class itself. This also enabled us to
remove several column classes completely, as they no longer had any
meaningful behavior of their own.
Merge pull request #15201 from sgrif/sg-types-postgresql

Have Postgres OID types inherit from general types
make the each visitor top-down left-right
prepopulate the dispatch cache so we don't need the ThreadSafe cache.
Merge pull request #15187 from v-yarotsky/fix_confusing_delegation_exception

Fix confusing exception in ActiveSupport delegation
Merge pull request #15203 from sgrif/sg-delegate-type-cast

Replace `type_cast` case statement with delegation
Merge pull request #15191 from camsong/master

Distinguish rake assets:clobber from rake assets:clean

[ci skip]
Use the generic type map object for mysql field lookups
Merge pull request #15200 from sgrif/sg-type-map-mysql

Use the generic type map object for mysql field lookups