Crystallize erc-nicks-track-faces behavior

Crystallize erc-nicks-track-faces behavior

* etc/ERC-NEWS: Mention changes to `erc-track-faces-normal-list' and
`erc-track-faces-priority-list'.  Also mention new choice variant for
option `erc-nicks-track-faces', although that's arguably just a bug fix
because it makes good on previously unrealized behavior implied by the
doc strings.
* lisp/erc/erc-nicks.el (erc-nicks-skip-faces): Remove faces applied by
the `match' module, namely, `erc-current-nick-face', `erc-pal-face', and
`erc-fool-face'.  That module runs its hooks after `button' on
`erc-insert-modify-hook', and because `nicks' piggybacks on `button', it
can never encounter those faces while assaying.
(erc-nicks-track-faces): Update doc, and introduce new `t' value choice.
(erc-nicks-mode, erc-nicks-disable): Update removals from
`erc-track--alt-normals-function' to reflect recent renamings.
(erc-nicks--reject-uninterned-faces): Use helper.
(erc-nicks--oursp, erc-nicks--ours-p): Rename former to latter to
respect project style guidelines regarding predicates.
(erc-nicks-track-normal-max-rank): New variable.
(erc-nicks--check-normals, erc-nicks--assess-track-faces): Rename former
to latter, and change purpose to checking for "normals" membership,
ranks position, and incumbent face ownership.  Remove unused CONTENDERS
parameter.  Additionally, change behavior to consider replacing the
current mode-line face when it's not `nicks' owned if it's explicitly
ranked lower than `erc-default-face'.
(erc-nicks--track-prioritize, erc-nicks--track-always): New
complementary functions implementing the t and `prioritize' variants of
`erc-nicks-track-faces'.  Both make use of the factored-out
`erc-nicks--check-normals' logic.
(erc-nicks--setup-track-integration): Add `erc-nicks--track-always' to
`erc-track--alt-normals-function' when `erc-track-normal-faces' is t.
* lisp/erc/erc-track.el (erc-track--massage-nick-button-faces): Change
type of symbol property `erc-track--obsolete-faces' for options
`erc-track-faces-priority-list' and friends from a boolean to an alist.
(erc-track-faces-priority-list): Add new face for buttonized speakers.
(erc-track-faces-normal-list): Add new face for buttonized speakers.
Also add `erc-notice-face'.
(erc-track--priority-faces): New local variable to cache ranked faces
and complement `erc-track--normal-faces'.
(erc-track--setup): Initialize new `erc-track--priority-faces' variable,
and refactor.
(erc-track--alt-normals-function): Doc.
(erc-track--select-mode-line-face): Update expected type of `ranks'
parameter.
(erc-track-modified-channels): Fix wrong-type bug occurring when
`erc-track-ignore-normal-contenders-p' and
`erc-track-priority-faces-only' are both non-nil.  Also fix subtle
compatibility oversight regarding an empty face list returned by
`erc-track--collect-faces-in'.
* test/lisp/erc/erc-nicks-tests.el: Load helpers and fixtures library.
(erc-nicks-tests--track-faces): New function.
(erc-nicks-track-faces/prioritize, erc-nicks-track-faces/defer)
(erc-nicks-track-faces/nil, erc-nicks-track-faces/t): New tests.
* test/lisp/erc/erc-track-tests.el
(erc-track-tests--select-mode-line-face): Update expected type of mocked
parameter.
(erc-track-tests--modified-channels/baseline): New function.
(erc-track-modified-channels/baseline)
(erc-track-modified-channels/baseline/mention)
(erc-track-modified-channels/baseline/ignore)
(erc-track-modified-channels/baseline/mention/ignore)
(erc-track-modified-channels/priority-only-all/baseline)
(erc-track-modified-channels/priority-only-all/sans-notice): New tests.
* test/lisp/erc/resources/erc-tests-common.el
(erc-tests-common-track-modified-channels)
(erc-tests-common-track-modified-channels-sans-setup): New functions.
(Bug67767)

(cherry picked from commit 9906e34f973f15c0f96ebcfcc6ea4d1144bc6e8f)