ErrorHandler - Present more error info about MySQL connections

[totten]

Overview

Present more error info about MySQL connections. This may be most useful if you're debugging a failure
in MySQL-SSL.

Technical Details

This is a work-around for a quirk in DB_mysqli::connect() -- it suppresses warnings
generated by mysqli_real_connect(). But those can be useful!

Th work-around depends on your boot mode (Civi-first vs CMS-first).
It applies to Civi-first. For CMS-first, the CMS error-handler is active
at the critical moment -- and it doesn't have such a work-around.

I'm on the fence about merging this. This should be safe enough (very narrow
impact). But it would be cleaner (and probably better) to patch
DB_mysqli::connect() to simply allow warnings. (Or, failing that, buffer
the warnings -- and let them through if we hit any subsequent problems.)
Addressing that root cause would make it less sensitive to boot-mode.

Of course, warnings have been suppressed for so long... it's hard to know if
we might create some backlash from it...

[demeritcowboy]

I'd lean towards removing the @. I'm always leaning towards that.

But also is this a php 7 vs 8 thing? See red box at https://www.php.net/manual/en/language.operators.errorcontrol.php

[totten]

I'd lean towards removing the @. I'm always leaning towards that.

It is evil...

But also is this a php 7 vs 8 thing? See red box at https://www.php.net/manual/en/language.operators.errorcontrol.php

Oh, good link. I think that means the problem is generally worse on php7. But for MySQL SSL errors (specifically), it reports the messages with E_WARNING. So the @ operator suppresses them on both php7+php8.