Adaptive fill mode broken in docstring

When filling in a docstring, there is no proper adaptive filling and it always seems to fill to the beginning column of the docstring. This problem has annoyed me for more than 5 years, so I stepped a bit through the debugger, but I don't understand Emacs Lisp well enough to provide a proper fix.

```
An arg - asdfasdfasd sadf as dfas df asdf asdf as df as df asd
fas df asdf asdf asdf as df asd fa sd fa sdf as df asdf as dfa sdf
```

Put the cursor somewhere into the indented section and press M-q. In Clojure mode, it will ruin the indentation. Proper adaptive filling will cut `as dfa sdf` and put in on the next line at col 9.

My best solution so far is to set `adaptive-fill-function` to `ignore` and `fill-paragraph-function` to `nil`. So far, I haven't observed any adverse side effects but sure it breaks something.

In general, there seems to be a bunch of logic implemented around docstrings in Clojure mode, but it is not very well documented and probably not working properly. Probably one could draw inspiration for how docstring indentation is solved in other LISP major modes.

I noticed that in Emacs Lisp for instance, docstrings have no special indentation behavior, and in Clojure there are two spaces prepended to each line. Its a weird convention but it seems to be somehow rooted in Clojure core? Is that what all the logic is about? Maybe getting rid of that is too much to ask for, but it would be nice if you can make adaptive filling work.

```
;;; Workaround, use at your own risk
(add-hook 'clojure-mode-hook
(lambda ()
(interactive)
(setq-local fill-paragraph-function nil)
(setq-local adaptive-fill-function 'ignore)))
```

Riproduci il problema in Clojure mode posizionando il cursore nella sezione di docstring rientrata e premendo M-q. Leggi la logica di riempimento relativa a docstring che coinvolge adaptive-fill-function e fill-paragraph-function, quindi confrontala con quella di altre modalità principali Lisp. Il lavoro è completo quando il riempimento adattivo posiziona il testo mandato a capo con il rientro corretto senza richiedere il workaround segnalato.

Scritto dal modello di indicizzazione a partire dal testo della issue.