[4.x] Drop tenant databases on `migrate:fresh` (#971)

* Test that `migrate:fresh` deletes tenant databases

* Delete tenants on `migrate:fresh`

* Fix code style (php-cs-fixer)

* Add config key for dropping tenant databases on `migrate:fresh`

* Add MigrateFreshOverride

* Try to override `migrate:fresh` in TenancyServiceProvider

* Update `migrate:fresh` test

* Fix code style (php-cs-fixer)

* Drop tenant databases by default

* Change `migrate:fresh` test to test if the tenant DBs are dropped by default

* Override `migrate:fresh` by extending `FreshCommand` in TenancyServiceProvider

* Update MigrateFreshOverride

* Fix code style (php-cs-fixer)

* Fix commands test

* Simplify handle method

* Fix code style (php-cs-fixer)

* Don't drop tenant DBs on migrate:fresh by default

* Change command overriding

* Update migrate:fresh test

* always register MigrateFreshOverride

* misc

Co-authored-by: PHP CS Fixer <phpcsfixer@example.com>
Co-authored-by: Samuel Štancl <samuel.stancl@gmail.com>