New deprecation Warning alternative

We were adding CRM_Core_Error::deprecationWarning to code that we wanted to be avoided. It was discussed in matter-most that it was a bit inaccurate so the bar for deprecating code became that we had to agree a new function first.

I pretty much stopped deprecating code after that but the deprecation process has been really helpful and the helper is much more grepable - in the meantime I'll switch back to

Civi::log()->warning("$className needs to be regenerated. Missing getEntityTitle method.", ['civi.tag' => 'deprecated']);