Misc code improvements and optimizations

Author: javiereguiluz

Dumper.php

@@ -146,7 +146,7 @@ private function dumpTaggedValue(TaggedValue $value, int $inline, int $indent, i
     {
         $output = sprintf('%s!%s', $prefix ? $prefix.' ' : '', $value->getTag());
 
-        if (Yaml::DUMP_MULTI_LINE_LITERAL_BLOCK & $flags && \is_string($value->getValue()) && false !== strpos($value->getValue(), "\n") && false === strpos($value->getValue(), "\r\n")) {
+        if (Yaml::DUMP_MULTI_LINE_LITERAL_BLOCK & $flags && \is_string($value->getValue()) && str_contains($value->getValue(), "\n") && !str_contains($value->getValue(), "\r\n")) {
             // If the first line starts with a space character, the spec requires a blockIndicationIndicator
             // http://www.yaml.org/spec/1.2/spec.html#id2793979
             $blockIndentationIndicator = (' ' === substr($value->getValue(), 0, 1)) ? (string) $this->indentation : '';