Review Request: LOG4J2-3075 Fix formatting of nanoseconds in JsonTemplateLayout.

Hello, I have pushed a branch (#495 ) incorporating a fix for the formatting of nanoseconds in JsonTemplateLayout. In a nutshell, FixedDateFormat and FastDateFormat support only upto millisecond precision. Hence, I try to employ the following form

JDK 17 Early Access build 23 is available

Hi Ralph, ** *OpenJDK 17 Early Access build 23 is now available at *_*https://jdk.java.net/17* _ * These early-access , open-source builds are provided under the o GNU General Public License, version 2, with the Classpath Exception