Add text props for CTCP messages and speakers in ERC

* etc/ERC-NEWS: Mention reduction in boldness of `erc-notice-face' and
`erc-action-face'.
* lisp/erc/erc-fill.el (erc-fill-spaced-commands,
erc-fill--spaced-commands): Rename former to latter and demote from
user option to internal variable.
(erc-fill): Change `erc-fill-spaced-commands' to
`erc-fill--spaced-commands'.
(erc-fill--wrap-continued-message-p): Use more precise `erc-ctcp' text
prop instead of face-based heuristic to detect CTCP ACTION message.
(erc-fill--wrap-action-dedent-p): New variable to toggle whether
`line-prefix' is applied to CTCP ACTION messages.  This exists less
to accommodate user preferences and more for third-party code that
assumes the first non-whitespace span in every message is a nick.
(erc-fill-wrap): Look for `erc-speaker' property before falling back
on word at point.  Use `erc-ctcp' to detect CTCP ACTION messages.
* lisp/erc/erc.el (erc-notice-face, erc-action-face): Prefer weight of
`semi-bold' when available so that buttonization is at least somewhat
perceptible in notices and action messages.
(erc-send-action): Ensure nickname passed to `erc-display-message' has
`erc-speaker' property and `erc-ctcp' ACTION property.
(erc--own-property-names): Add `erc-speaker' to lineup.
(erc-format-privmessage): Don't clobber `erc-nick-prefix-face'.  That
is, retain face applied to a leading stretch of characters in the
`nick' parameter, but continue to discard trailing faces.
(erc-format-my-nick, erc-ctcp-query-ACTION): Add new text property
`erc-speaker' to the nick portion of the formatted speaker label.  Do
this to assist modules, like `button' and `match', that currently
re-parse speakers in inserted messages.
(erc-process-ctcp-query): Add `erc-ctcp' property to entire message
before insertion hooks see it.
* test/lisp/erc/erc-fill-tests.el (erc-fill-tests--compare): Warn
about certain unreliable comparisons if generalizing helper for use by
other modules.
* test/lisp/erc/erc-tests.el (erc-tests--equal-including-properties):
New helper compat macro.
(erc-format-privmessage): New test.  (Bug#64301)

test/lisp/erc/erc-fill-tests.el

@@ -153,7 +153,10 @@
         (with-temp-file expect-file
           (insert repr))
       (if (file-exists-p expect-file)
-          ;; Compare set-equal over intervals
+          ;; Compare set-equal over intervals.  This comparison is
+          ;; less useful for messages treated by other modules because
+          ;; it doesn't compare "nested" props belonging to
+          ;; string-valued properties, like timestamps.
           (should (equal-including-properties
                    (read repr)
                    (read (with-temp-buffer

test/lisp/erc/erc-tests.el

@@ -1443,6 +1443,49 @@
     (kill-buffer "ExampleNet")
     (kill-buffer "#chan")))
 
+(defmacro erc-tests--equal-including-properties (a b)
+  (list (if (< emacs-major-version 29)
+            'ert-equal-including-properties
+          'equal-including-properties)
+        a b))
+
+(ert-deftest erc-format-privmessage ()
+  ;; Basic PRIVMSG
+  (should (erc-tests--equal-including-properties
+           (erc-format-privmessage (copy-sequence "bob")
+                                   (copy-sequence "oh my")
+                                   nil 'msgp)
+           #("<bob> oh my"
+             0 1 (font-lock-face erc-default-face)
+             1 4 (erc-speaker "bob" font-lock-face erc-nick-default-face)
+             4 11 (font-lock-face erc-default-face))))
+
+  ;; Basic NOTICE
+  (should (erc-tests--equal-including-properties
+           (erc-format-privmessage (copy-sequence "bob")
+                                   (copy-sequence "oh my")
+                                   nil nil)
+           #("-bob- oh my"
+             0 1 (font-lock-face erc-default-face)
+             1 4 (erc-speaker "bob" font-lock-face erc-nick-default-face)
+             4 11 (font-lock-face erc-default-face))))
+
+  ;; Prefixed PRIVMSG
+  (let* ((user (make-erc-server-user :nickname (copy-sequence "Bob")))
+         (cuser (make-erc-channel-user :op t))
+         (erc-channel-users (make-hash-table :test #'equal)))
+    (puthash "bob" (cons user cuser) erc-channel-users)
+
+    (should (erc-tests--equal-including-properties
+             (erc-format-privmessage (erc-format-@nick user cuser)
+                                     (copy-sequence "oh my")
+                                     nil 'msgp)
+             #("<@Bob> oh my"
+               0 1 (font-lock-face erc-default-face)
+               1 2 (font-lock-face erc-nick-prefix-face help-echo "operator")
+               2 5 (erc-speaker "Bob" font-lock-face erc-nick-default-face)
+               5 12 (font-lock-face erc-default-face))))))
+
 (defvar erc-tests--ipv6-examples
   '("1:2:3:4:5:6:7:8"
     "::ffff:10.0.0.1" "::ffff:1.2.3.4" "::ffff:0.0.0.0"