[Config] Add Application Packages

[jackshirazi]

Classic agent link

• https://www.elastic.co/guide/en/apm/agent/java/current/config-stacktrace.html#config-application-packages

What it does

Determines whether a stack trace frame is an in-app frame or a library frame for better UI experience

Implementation difficulty, location, and dynamism

• This is implemented in the classic agent by giving each stack element a true/false value depending on whether it is in/out of the packages. Currently the UI only displays code.stacktrace as a string. We'd need to add additional support in the UI first, either by having it take into account a true/false array, or passing the package list and have the UI do the work.
• It cannot be contributed upstream
• It can be dynamic