Clean-up deprecated non-standard cast names

I found only one tool to fix it https://github.com/PHP-CS-Fixer/PHP-CS-Fixer/blob/master/doc/rules/cast_...

There’s a rule in slevomat/coding-standard:

https://github.com/slevomat/coding-standard/blob/master/doc/php.md#slevo...

Thank you @jacktonkin it can catch!

andypost → closed merge request !12983

Including this as a coding standards rule makes sense, and to me it doesn't need to run through the Coding Standards Committee, because it's a language-level decision and there's nothing we can change or document about it.

Since this passes the new rule, we can be sure we caught all the changes.

Committed fc1872a and pushed to 11.x. Thanks!

Backported to 11.2.x,10.6.x,10.5.x without the PHPCS rule
Committed 71976f3 and pushed to 11.2.x. Thanks!
Committed e35092a and pushed to 10.6.x. Thanks!
Committed 2d8538d and pushed to 10.5.x. Thanks!