[Active Record] Renamed private methods create_record and update_record

 This is to ensure that they are not accidentally called by the app code.
 They are renamed to _create_record and _update_record respectively.
 Closes #11645
Do not overwrite selected and disabled attributes
Fix polymorphic preloads on NOT NULL _type columns.

Defer to Association#klass instead of having a custom/duplicate code.
Simplify Preloader#grouped_records code.

The new method relies on AR::Associations::Association knowing about both reflection and a model class.

AR::Base#association now raises a descriptive error when trying to access non-existent associations. Previously it would blow up with a confusing NoMethodError: undefined method `association_class' for nil:NilClass.
Tiny doc fix for Strong Parameters

- accepts_nested_attribute_for -> accepts_nested_attributes_for
Merge pull request #14535 from iancanderson/patch-1

Tiny doc fix for Strong Parameters
refactor, put `PostgreSQLColumn` into `column.rb`.

We have `connection_adapters/column.rb` so it's easier to remember
that the column in in a separate file.
Merge pull request #14532 from thedarkone/polymorphic-preload-fix

Fix polymorphic preloads on NOT NULL _type columns
Fix release task

Add a parentheses.
related: b4c96490eeb1fbb944e116c7703dd528b37fc08a
Merge pull request #14542 from arthurnn/fix_release_task

Fix release task
Add test for selected and disabled custom attributes in options_for_select
Merge pull request #14539 from lparedes/master

Do not overwrite selected and disabled attributes
add capture_sql method to compare sql statements and compare

Other methods compare specific patterns, this method outputs
the actual sql query that is generated.
add test to compare sql statements in delete_all query

delete_all sql if an association is not loaded should behave
the same as if the association is loaded. This test ensures
the SQL statements are exactly the same.
fix delete_all to remove records directly

When delete_all is run on a CollectionProxy and has a
dependency of delete_all the SQL that is produced has an IN
statement. (DELETE FROM `associated_model` where `associated_model`
.`parent_id` = 1 AND `associated_model`.`id` IN (1, 2, 3...)).
This only happens if the association is not loaded (both loaded
and non-loaded delete_all should behave the same. This is a huge
problem when it comes to deleting many records because the query
becomes very slow. Instead the SQL produced should be (DELETE FROM
`assoicated_model` where `associated_model`.`parent_model_id`=1).

I fixed this by making sure the check for loaded and destroy also
makes sure that the dependent is not delete_all, so the conditional
goes to the else and deletes the records directly without the IN
statement.
Merge pull request #14546 from eileencodes/fix_delete_all_to_not_use_IN_statement

Fix delete all to not produce sql in statement
Make AS::SafeBuffer#prepend act like String#prepend

Make `#prepend` method modify instance in-place and return self
instead of just returning modified value. That is exactly what
`#prepend!` method was doing previously, so it's deprecated from
now on.
refactor assert_sql query to reuse capture_sql

set assert_sql to reuse the capture_sql method from above
instead of repeating the code

in response to comments on issue #14546
Merge pull request #14548 from eileencodes/refactor_capture_sql_in_tests

refactor assert_sql query to reuse capture_sql
PostgreSQL determine `Column#type` through corresponding OID. #7814

I ran the whole test suite and compared the old to the new types.
Following is the list of types that did change with this patch:

```
DIFFERENT TYPE FOR mood: NEW: enum, BEFORE:
DIFFERENT TYPE FOR floatrange: NEW: floatrange, BEFORE: float
```

The `floatrange` is a custom type. The old type `float` was simply a coincidence
form the name `floatrange` and our type-guessing.