Merge branch 'hotfix/#6869-stdlib-hydrator-should-only-hydrate-public-properties'

Close #6869
fix #6814: ignore php 5.5 scalar class name resolution
#6814 #6946 - checking against `PHP_VERSION_ID` as `version_compare()` is unreliable
#6814 #6946 - adding missing `@group` annotations to newly introduced test cases
Merge branch 'hotfix/#6946-ignore-php-5-5-scalar-class-name-resolution' into develop

Close #6946
Close #6814
Forward port #6946
Forward port #6814