bug#69657: Missing imenu entries with eglot

[Sebastian Poeplau]

> I understand Sebastian wants to see an extra top-evel ("Foo" . 1) there
> or something, but that leads to two entries with duplicate names and imenu
> just doesn't like that (if I apply the patch I just can't go to 'bar' with M
> -x imenu), neither do some of its clients.

What about naming the separate entry differently, e.g., "Foo (top)"?
I'll certainly look into using the breadcrumb metadata instead, but that
doesn't help users of plain imenu.

> This is way Eglot emits "breadcrumb"-friendly cookies to overcome imenu's
> limitations.   Using breadcrumb i can jump to Foo and Foo > bar just
> fine (using
> `M-x breadcrumb-jump`).

Thanks for the hint, I didn't know about `breadcrumb-jump'; I'd only
used the headline feature before.

> Anyway, if users don't like Eglot's imenu function, they can use something
> else.  Eglot's imenu is different from c++-ts-mode, and afaik c++-ts-mode's is
> already different from c++-mode's.  I wouldn't install this patch though,
> teach other UIs about those optional cookies seems like a better deal that
> doesn't break stuff.

I wonder why I did get separate entries in consult-imenu with pylsp
though. I'll have to give it another look, but it seems to me that in
this case (e.g., with SymbolInformation objects) eglot's imenu function
returns data that (a) works with plain imenu and (b) gives me what I
expect with consult-imenu.