Stricter DateTimeParser for known formats (fixes #569) (#4330)

* GH #569: Cherry pick and correct code from devel-experimental.

* GH #569: Add missing timezone codes.

* enh(Foundation): DateTimeParser: stricter checks of timezones, more tests for invalid inputs. (#569)

* enh(Foundation): Small fixes of issues detected by CodeQL

---------

Co-authored-by: Alex Fabijanic <alex@pocoproject.org>

Foundation/include/Poco/DateTimeParser.h

@@ -53,6 +53,8 @@ class Foundation_API DateTimeParser
 	/// If more strict format validation of date/time strings is required, a regular
 	/// expression could be used for initial validation, before passing the string
 	/// to DateTimeParser.
+	/// TODO: Correct description
+
 {
 public:
 	static void parse(const std::string& fmt, const std::string& str, DateTime& dateTime, int& timeZoneDifferential);