adopt systemProperty tag in javadoc

to allow indexing & searching of defined properties, see https://docs.oracle.com/en/java/javase/21/docs/specs/javadoc/doc-comment-spec.html#systemproperty

Start by reviewing the repository's Javadoc comments and the linked Java 21 doc-comment specification for the systemProperty tag. Identify the comments that define system properties; done means those properties use the tag consistently and can be indexed and searched as intended.

Written by the indexing model from the issue text.