dwarf2read: Get rid of VEC (dwarf2_section_info_def)

dwarf2read: Get rid of VEC (dwarf2_section_info_def)

This patch removes uses of VEC (dwarf2_section_info_def) in favor of
std::vector<dwarf2_section_info>.  The conversion is relatively
straightforward, no function changes are intended.

gdb/ChangeLog:

	* dwarf2read.h (dwarf2_section_info_def): Remove.
	(DEF_VEC_O (dwarf2_section_info_def)): Remove.
	* dwarf2read.c (struct dwo_sections) <types>: Change type to
	std::vector<dwarf2_section_info>.
	(struct dwo_file) <~dwo_file>: Remove.
	(dwarf2_per_objfile::~dwarf2_per_objfile): Don't manually free
	types field.
	(dwarf2_per_objfile::locate_sections): Adjust to std::vector.
	(dwarf2_read_debug_names): Likewise.
	(create_debug_types_hash_table): Change parameter type to
	array_view, adjust code accordingly.
	(dwarf2_locate_dwo_sections): Adjust to std::vector.
	(partial_die_info::fixup): Likewise.
	(determine_prefix): Likewise.
	* dwarf-index-write.c (write_psymtabs_to_index): Adjust.