analyzer: Restore g++ 4.8 bootstrap; use std::move to return std::unique_ptr.

analyzer: Restore g++ 4.8 bootstrap; use std::move to return std::unique_ptr.

This patch restores bootstrap when using g++ 4.8 as a host compiler.
Returning a std::unique_ptr requires a std::move on C++ compilers
(pre-C++17) that don't guarantee copy elision/return value optimization.

2024-06-08  Roger Sayle  <roger@nextmovesoftware.com>

gcc/analyzer/ChangeLog
	* constraint-manager.cc (equiv_class::make_dump_widget): Use
	std::move to return a std::unique_ptr.
	(bounded_ranges_constraint::make_dump_widget): Likewise.
	(constraint_manager::make_dump_widget): Likewise.
	* program-state.cc (sm_state_map::make_dump_widget): Likewise.
	(program_state::make_dump_widget): Likewise.
	* region-model.cc (region_to_value_map::make_dump_widget): Likewise.
	(region_model::make_dump_widget): Likewise.
	* region.cc (region::make_dump_widget): Likewise.
	* store.cc (binding_cluster::make_dump_widget): Likewise.
	(store::make_dump_widget): Likewise.
	* svalue.cc (svalue::make_dump_widget): Likewise.