Fix documentation
#6895 - `Zend\Log\Processor\Backtrace#getBacktrace()` returns an `array` of `array`s
Merge branch 'hotfix/#6895-correct-log-processor-get-backtrace-return-type'

Close #6895
Fixes CS : unused use
Merge branch 'cs/#6629-remove-unused-code'

Close #6629
Fixes Zend\Json\Json's composer.json containing single backslash
Merge branch 'hotfix/#6891-#6778-composer-json-string-escaping'

Close #6891
PHPCS fixes for Zend\File