Remove duplicated SKIP checks from mysqli tests (#7858)

Fix some more CLEANUP sections

Port skipif.inc files to EXTENSIONS

Fix #80329: Add option to specify LOAD DATA LOCAL white list folder

* allow the user to specify a folder where files that can be sent
via LOAD DATA LOCAL can exist
* add mysqli.

Fix #80329: Add option to specify LOAD DATA LOCAL white list folder

* allow the user to specify a folder where files that can be sent
via LOAD DATA LOCAL can exist
* add mysqli.local_infile_directory for mysqli
(ignored if mysqli.allow_local_infile is enabled)
* add PDO::MYSQL_ATTR_LOCAL_INFILE_DIRECTORY for pdo_mysql
(ignored if PDO::MYSQL_ATTR_LOCAL_INFILE is enabled)
* add related tests
* fixes for building with libmysql 8.x
* small improvement in existing tests
* update php.ini-[development|production] files

Closes GH-6448.

Co-authored-by: Nikita Popov <nikic@php.net>

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