Encode/decode INI properties in IniFileChain since the encoding/decoding is used to avoid issues w/ parse_ini_file() use.

Move Config::encodeValues/Config::decodeValues from Config to IniFileChain since they are vital to correctly storing/loading settings w/o strange bugs.

Refs #7312, fix bug where config file is saved w/ sections in incorrect order. Bug occurs due to incorrect sorting that sorts sections according to which files they appear in, but not where they appear in individual files.

Fix issue where reference not returned by IniFileChain::get when settings file is completely empty and add test case. Also add type hint to IniFileChain::__construct.

Fix unit test, make array settings being overwritten in default settings file chain the expected behavior.