Define if-let* and derivatives as aliases for if-let etc

Define if-let* and derivatives as aliases for if-let etc

This commit reverts declaring `if-let' and `when-let' obsolete in
favor of the new `if-let*' and `when-let*' versions because of the
compiler warning mess (Bug#30039).  Instead we make foo-let* aliases
for foo-let.  The old single-tuple variable spec case is still
supported for backward compatibility.
* lisp/emacs-lisp/subr-x.el (if-let, when-let): Don't declare
obsolete.  Tweak edebug specs.
(and-let): Renamed from `and-let*' for compatibility with the names
`if-let' and `when-let'.
(if-let*, when-let*, and-let*): Define as aliases for `if-let',
`when-let' and `and-let'.
* test/lisp/emacs-lisp/subr-x-tests.el (if-let-single-tuple-case-test)
(when-let-single-tuple-case-test): New tests for the single-binding
tuple case.
In the whole file, prefer the names without "*".