Replace use of if-let and when-let, obsolete in Emacs 31.0.50

[spwhitton]

Hello,

if-let and when-let are obsolete on the trunk. Here is an update for transient.

If it is convenient for you, would you consider making a release, and importing it into emacs.git? This would squelch all the byte compiler warnings.

Thanks!

[tarsius]

In https://debbugs.gnu.org/cgi/bugreport.cgi?bug=+73853 @spwhitton said:

I believe there was a previous attempt to deprecate them but it had to
be backed out. But maybe now is the time to try again.

And I passionately hope this deprecation gets reverted once again.

I haven't slept in more than a day, so that's all for now. I'll probably write a salty reply in that thread in a few days.

I am closing this because I do not intend to merge it.

And I am locking it because just yesterday I realized that it is high time to take some time off from the daily grind of jumping right on the stuff other people shovel onto my todo list almost every day. Being forced to make a stand in this discussion is the exact opposite of that.

[tarsius]

I've posted my response at https://debbugs.gnu.org/cgi/bugreport.cgi?bug=+73853#130.