Rework eln deletion strategy for new eln-cache folder structure

Rework eln deletion strategy for new eln-cache folder structure

When recompiling remove the corresponding stale elns found in the
`comp-eln-load-path'.

When removing a package remove the corresponding elns too.

On Windows both of these are performed only when possible, when it's
not the file is renamed as .eln.old and a last attempt to remove this
is performed closing the Emacs session.  When a file being deleted was
loaded by multiple Emacs sessions the last one being closed should
delete it.

	* lisp/emacs-lisp/comp.el (comp-clean-up-stale-eln): New function.
	(comp-delete-or-replace-file): Rename from
	`comp--replace-output-file' and update so it can be used for
	replacing or deleting shared libs safetly.

	* lisp/emacs-lisp/package.el (package--delete-directory): When
	native compiled just call `comp-clean-up-stale-eln' for each
	eln file we want to clean-up.

	* src/alloc.c (cleanup_vector): Call directly the dynlib_close.

	* src/comp.c (syms_of_comp): Update for comp_u->cfile removal.
	Make 'all_loaded_comp_units_h' key-value weak as now the key will
	be the filename.
	(load_comp_unit): Register the compilation unit only when the load
	is fully completed.
	(register_native_comp_unit): Make the key of
	all_loaded_comp_units_h the load filename.
	(eln_load_path_final_clean_up): New function.
	(dispose_comp_unit)
	(finish_delayed_disposal_of_comp_units)
	(dispose_all_remaining_comp_units)
	(clean_package_user_dir_of_old_comp_units): Remove.
	(Fcomp__compile_ctxt_to_file): Update for
	`comp--replace-output-file' -> `comp-delete-or-replace-file'
	rename.

	* src/comp.h (dispose_comp_unit)
	(finish_delayed_disposal_of_comp_units)
	(dispose_all_remaining_comp_units)
	(clean_package_user_dir_of_old_comp_units): Remove.
	(eln_load_path_final_clean_up): Add.
	(struct Lisp_Native_Comp_Unit): Remove cfile field.

	* src/emacs.c (Fkill_emacs): Call 'eln_load_path_final_clean_up'.

	* src/pdumper.c (dump_do_dump_relocation): Do not set comp_u->cfile.