Replace code examples in Javadoc with JEP 413: Code Snippets

The code examples in the library are currently put in a `<pre>{@code }</pre>` block, which is additionally higlighted via a _proprietary_ code highlighter. In this ticket, all code example should be using the new `{@snippet : }` Javadoc feature. The code examples should also be compileable, so that is no longer the case to have invalid examples in the Javadoc.