fn:random-number-generator not spec compliant

[line-o]

What is the problem

The function fn:random-number-generator is not compliant to the xquery 3.1 specification.

Specifically:

1. The seed can be of type xs:anyAtomic but only xs:number is supported because it is internally cast to java.long

   exist/exist-core/src/main/java/org/exist/xquery/functions/fn/FnRandomNumberGenerator.java

   Line 43 in cdefdee

   random = new Random(args[0].itemAt(0).toJavaObject(long.class));

2. There is a side-effect with the function returned in the next key.
   

   exist/exist-core/src/main/java/org/exist/xquery/functions/fn/FnRandomNumberGenerator.java

   Line 84 in cdefdee

   return buildResult(context, random);

What did you expect

The implementation to be spec compliant.

Describe how to reproduce or add a test

You can find the tests in #3072

Context information

• eXist-db 5.0.x /
• Java
• MacOs 10.14.x (64 bit)
• clone from latest develop
• no custom changes