[3.0] Print the registration errors that carry their own words

[albertlast]

Description

Refuse a registration for a weak password and the form says "The following errors
were detected in your registration. Please correct them to continue:" above a
bullet with nothing in it.

$ # register with passwrd1=password
<div class="errorbox">
    <span>The following errors were detected in your registration…</span>
    <ul>
        <li></li>
    </ul>
</div>

Each entry in $reg_errors is [kind, text, log, args], where the kind is
'lang' for a language key and 'done' for a finished sentence. The comment
directly above the loop says so:

/* Note for each error:
    0 = 'lang' if it's an index, 'done' if it's clear text.
    1 = The text/index. … */
$message = Lang::getTxt($error[1], (array) ($error[3] ?? []), file: 'Errors');

The loop never reads $error[0]. It looks every error up in Errors, a 'done'
error is not a key there, getTxt() returns an empty string for a key it cannot
find, and that empty string is the bullet. 2.1 read the kind here.

What reaches it. Register2 builds ['done', $password_error, false]
whenever validatePassword() hands back something that is not a language key —
which is the zxcvbn feedback, so every strength rejection except short. It is
also how Security::validateUsername() reports a name already in use.

What changes

One line: a 'done' error prints its own words.

Testing

Registering with password:

This is a top-10 common password.
Add another word or two. Uncommon words are better.

with abc, unchanged: "Your password must be at least 6 characters long."
A clean registration still succeeds.

Issues References (Fixes|Related|Closes)

Related to #7933