Memory settings in `package.yaml`

[JaroslavTulach]

• based on ENSO_JVM_OPTS changes its meaning depending on jvm mode #13279 report
• we want to give Enso end users other alternative than ENSO_JVM_OPTS
• they only care about memory settings so far
• solution: let them specify memory settings in package.yaml

Originally posted by @JaroslavTulach in #13279