Improve indexing of system properties

Multiple mentions of a system property in a single type are not distinguishable from one another, nor are they informative.

For example, consider the "javax.rmi.ssl.client.enabledCipherSuites" system property. This property is mentioned twice in the javax.rmi.ssl.SslRMIClientSocketFactory type. Once in the top-level type documentation and once in the createSocket method.

This is how it is represented on the index page at https://docs.oracle.com/en/java/javase/13/docs/api/index-files/index-10.html :

javax.rmi.ssl.client.enabledCipherSuites - Search tag in javax.rmi.ssl.SslRMIClientSocketFactory
System Property
javax.rmi.ssl.client.enabledCipherSuites - Search tag in javax.rmi.ssl.SslRMIClientSocketFactory
System Property

The same goes for the "interactive search".