New KT for ksqlDB lambda functions

ksqlDB 0.17 introduced the ability to use simple in-line functions vs. having to provide a UDF https://www.confluent.io/blog/announcing-ksqldb-0-17-0-new-features-and-updates/#lambda-functions

Start by reading the linked ksqlDB 0.17 announcement, especially the lambda-functions section, then inspect the repository's existing tutorial structure for the appropriate entry point. Done should be a complete tutorial explaining simple inline functions rather than requiring a UDF, with the relevant example and validation steps documented.

Written by the indexing model from the issue text.