Don't calculate new values when using the private context callback.

Don't calculate new values when using the private context callback.

When using rangers private callback mechanism to provide context
to fold_stmt calls, we are only suppose to be using the cache in read
only mode, never calculate new values.

	gcc/
	PR tree-optimization/103122
	* gimple-range.cc (gimple_ranger::range_of_expr): Request the cache
	entry with "calulate new values" set to false.

	gcc/testsuite/
	* g++.dg/pr103122.C: New.