fortran: array descriptor: Move accessor functions to a separate file [PR122521]

Move existing descriptor getters and setters to a new file.

	PR fortran/122521

gcc/fortran/ChangeLog:

	* Make-lang.in (F95_OBJS): Add fortran/trans-descriptor.o to the
	list of objects.
	* trans-array.cc: Include new header.
	(gfc_get_descriptor_field, gfc_conv_descriptor_data_get,
	gfc_conv_descriptor_data_set, gfc_conv_descriptor_offset,
	gfc_conv_descriptor_offset_get, gfc_conv_descriptor_offset_set,
	gfc_conv_descriptor_dtype, gfc_conv_descriptor_span,
	gfc_conv_descriptor_span_get, gfc_conv_descriptor_span_set,
	gfc_conv_descriptor_rank, gfc_conv_descriptor_version,
	gfc_conv_descriptor_elem_len, gfc_conv_descriptor_attribute,
	gfc_conv_descriptor_type, gfc_get_descriptor_dimension,
	gfc_conv_descriptor_dimension, gfc_conv_descriptor_token,
	gfc_conv_descriptor_subfield, gfc_conv_descriptor_stride,
	gfc_conv_descriptor_stride_get, gfc_conv_descriptor_stride_set,
	gfc_conv_descriptor_lbound, gfc_conv_descriptor_lbound_get,
	gfc_conv_descriptor_lbound_set, gfc_conv_descriptor_ubound,
	gfc_conv_descriptor_ubound_get, gfc_conv_descriptor_ubound_set):
	Move functions ...
	* trans-descriptor.cc: ... to this new file.
	* trans-array.h (gfc_get_descriptor_offsets_for_info): Fix
	long line in declaration.
	(gfc_conv_descriptor_data_get, gfc_conv_descriptor_offset_get,
	gfc_conv_descriptor_span_get, gfc_conv_descriptor_dtype,
	gfc_conv_descriptor_rank, gfc_conv_descriptor_elem_len,
	gfc_conv_descriptor_version, gfc_conv_descriptor_attribute,
	gfc_conv_descriptor_type, gfc_get_descriptor_dimension,
	gfc_conv_descriptor_stride_get, gfc_conv_descriptor_lbound_get,
	gfc_conv_descriptor_ubound_get, gfc_conv_descriptor_token,
	gfc_conv_descriptor_data_set, gfc_conv_descriptor_offset_set,
	gfc_conv_descriptor_span_set, gfc_conv_descriptor_stride_set,
	gfc_conv_descriptor_lbound_set, gfc_conv_descriptor_ubound_set):
	Move declarations ...
	* trans-descriptor.h: ... to this new file.
	* trans-decl.cc: Include new header.
	* trans-expr.cc: Likewise.
	* trans-intrinsic.cc: Likewise.
	* trans-io.cc: Likewise.
	* trans-openmp.cc: Likewise.
	* trans-stmt.cc: Likewise.
	* trans.cc: Likewise.