Allow for class type coarray parameters. [PR77871]

gcc/fortran/ChangeLog:

	PR fortran/77871

	* trans-expr.cc (gfc_conv_derived_to_class): Assign token when
	converting a coarray to class.
	(gfc_get_tree_for_caf_expr): For classes get the caf decl from
	the saved descriptor.
	(gfc_get_caf_token_offset):Assert that coarray=lib is set and
	cover more cases where the tree having the coarray token can be.
	* trans-intrinsic.cc (gfc_conv_intrinsic_caf_get): Use unified
	test for pointers.

gcc/testsuite/ChangeLog:

	* gfortran.dg/coarray/dummy_3.f90: New test.