gdb: replace function pointer with `void *` data with function_view

Replace the function pointer + `void *` parameters of
dwarf2_fetch_die_loc_sect_off and dwarf2_fetch_die_loc_cu_off with a
function_view parameter.  Change call sites to use a lambda function.
This improves type-safety, so reduces the chances of errors.

gdb/ChangeLog:

	* read.h (dwarf2_fetch_die_loc_sect_off,
	dwarf2_fetch_die_loc_cu_off): Replace function pointer +
	`void *` parameter with function_view.
	* read.c (dwarf2_fetch_die_loc_sect_off,
	dwarf2_fetch_die_loc_cu_off): Likewise.
	* loc.c (get_frame_pc_for_per_cu_dwarf_call): Remove.
	(per_cu_dwarf_call): Adjust.
	(get_frame_address_in_block_wrapper): Remove.
	(indirect_synthetic_pointer): Adjust.
	(get_ax_pc): Remove.
	(dwarf2_compile_expr_to_ax): Adjust.

Change-Id: Ic9b6ced0c4128f2b75ca62e0ed638b0962a22859