Add text props for CTCP messages and speakers in ERC

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)