Implements a binary renderer for Pkl values, which is a lossless capturing of Pkl data.
This follows the pkl binary format that is already used with `pkl server` calls, and is
made available as a Java API and also an in-language API.
Also, introduces a binary parser into the corresponding `PObject` types in Java.
This change activates the `TYPESAFE_PROJECT_ACCESSORS` feature
preview in Gradle, and switches to such accessors instead of
string-based project references, where possible
Relates-To: apple/pkl#204
Signed-off-by: Sam Gammon <sam@elide.ventures>
