Add original_scope method

[zhuravel]

See discussion: 157986f#r105876563

[bogdan]

local variable with the same name as method name can be confusing:

Suggested change

	scope = original_scope
	driver.to_scope(scope)
	driver.to_scope(original_scope)

[zhuravel]

It is not the same.

See commit with your suggestion: https://github.com/zhuravel/datagrid/commit/d5e2362c3f7e70da950260cb21e1eac044e47f73
See how it breaks build: https://github.com/zhuravel/datagrid/actions/runs/4512413662

This is due to order in which Ruby evaluates code (or some other reason that I can’t comprehend after years of writing Ruby code), original_scope has to be called before driver.to_scope and not passed as an argument. These options work though:

scope = original_scope
driver.to_scope(scope)

original_scope.then do |scope|
  driver.to_scope(scope)
end