Providing prior implicit field name to db_column should be a noop

[Jacob Walls]

Similar to #31826, I would expect no migration changes detected when a db_column is added that matches the implicit field name. I tested with and without renaming the field on SQLite and MySQL 5.7.31. I'm not familiar enough with the review of #31826 to know whether these are distinct cases versus if it should be reopened.

class Apple(models.Model):
    core = models.BooleanField()

class Apple(models.Model):
    core_renamed = models.BooleanField(db_column='core')

Was apple.core renamed to apple.core_renamed (a BooleanField)? [y/N] y
Migrations for 'renamez':
  renamez/migrations/0002_rename_core_apple_core_renamed_and_more.py
    - Rename field core on apple to core_renamed
    - Alter field core_renamed on apple

python manage.py sqlmigrate renamez 0002 showing unnecessary SQL:

BEGIN;
--
-- Rename field core on apple to core_renamed
--
ALTER TABLE "renamez_apple" RENAME COLUMN "core" TO "core_renamed";
--
-- Alter field core_renamed on apple
--
ALTER TABLE "renamez_apple" RENAME COLUMN "core_renamed" TO "core";
COMMIT;

Without renaming the field, follow the same flow and get an AlterField migration without SQL:

BEGIN;
--
-- Alter field core on apple
--
COMMIT;