analyzer: improvements to region_model::get_representative_tree

analyzer: improvements to region_model::get_representative_tree

This patch extends region_model::get_representative_tree so that dumps
are able to refer to string literals, which I've found useful in
investigating a state-bloat issue.

Doing so uncovered a bug in the handling of views I introduced in
r10-7024-ge516294a1acb28aaaad44cfd583cc6a80354044e where the code was
erroneously using TREE_TYPE on the view region's type, rather than just
using its type, which the patch also fixes.

gcc/analyzer/ChangeLog:
	* analyzer.h (class array_region): New forward decl.
	* program-state.cc (selftest::test_program_state_dumping_2): New.
	(selftest::analyzer_program_state_cc_tests): Call it.
	* region-model.cc (array_region::constant_from_key): New.
	(region_model::get_representative_tree): Handle region_svalue by
	generating an ADDR_EXPR.
	(region_model::get_representative_path_var): In view handling,
	remove erroneous TREE_TYPE when determining the type of the tree.
	Handle array regions and STRING_CST.
	(selftest::assert_dump_tree_eq): New.
	(ASSERT_DUMP_TREE_EQ): New macro.
	(selftest::test_get_representative_tree): New selftest.
	(selftest::analyzer_region_model_cc_tests): Call it.
	* region-model.h (region::dyn_cast_array_region): New vfunc.
	(array_region::dyn_cast_array_region): New vfunc implementation.
	(array_region::constant_from_key): New decl.

gcc/testsuite/ChangeLog:
	* gcc.dg/analyzer/malloc-4.c: Update expected output of leak to
	reflect fix to region_model::get_representative_path_var, adding
	the missing "*" from the cast.