Add comp-cstr.el and comp-cstr-tests.el

Add comp-cstr.el and comp-cstr-tests.el

As the constraint logic of the compiler is not trivial and largely
independent from the rest of the code move it into comp-cstr.el to
ease separation and maintainability.

This commit improve the conversion type
specifier -> constraint for generality.

Lastly this should help with bootstrap time as comp.el compilation
unit is slimmed down.

	* lisp/emacs-lisp/comp-cstr.el: New file.
	(comp--typeof-types, comp--all-builtin-types): Move from comp.el.
	(comp-cstr, comp-cstr-f): Same + rename.
	(comp-cstr-ctxt): New struct.
	(comp-supertypes, comp-common-supertype-2)
	(comp-common-supertype, comp-subtype-p, comp-union-typesets)
	(comp-range-1+, comp-range-1-, comp-range-<, comp-range-union)
	(comp-range-intersection): Move from comp.el.
	(comp-cstr-union-no-range, comp-cstr-union): Move from comp.el and
	rename.
	(comp-cstr-union-make): New function.
	(comp-type-spec-to-cstr, comp-cstr-to-type-spec): Move from
	comp.el, rename it and rework it.

	* lisp/emacs-lisp/comp.el (comp-known-func-cstr-h): Rework.
	(comp-ctxt): Remove two fields and include `comp-cstr-ctxt'.
	(comp-mvar, comp-fwprop-call): Update for `comp-cstr' being
	renamed.
	(comp-fwprop-insn): Use `comp-cstr-union-no-range' or
	`comp-cstr-union'.
	(comp-ret-type-spec): Use `comp-cstr-union' and rework.

	* test/lisp/emacs-lisp/comp-cstr-tests.el: New file.
	(comp-cstr-test-ts, comp-cstr-typespec-test): New functions.
	(comp-cstr-typespec-tests-alist): New defconst to generate tests
	on.
	(comp-cstr-generate-tests): New macro.

	* test/src/comp-tests.el (comp-tests-type-spec-tests): Update.
	(ret-type-spec): Initialize constraint context.