support for reading JAVA_TOOL_OPTIONS for port

[rverma-jm]

Basic framework to allow debug port through environment variables on original pod.

[solo-build-bot[bot]]

Waiting for approval from someone in the solo-io org to start testing.

[kdorosh]

/test

[mitchdraft]

@rverma-jm I like the idea of this feature but am not super comfortable with the approach. I would prefer a solution that did not involve printenv or changing the signature of the Attach function.

• I would like to hear @yuval-k's thoughts on passing the environment variables around and whether it's better to read the environment variables from the container spec or through printenv
• As an alternative to the modified Attach function, I think it would would be cleaner for the debuggers to optionally implement a "ParseEnvironment" interface which would define the exact environment variables relevant to each debugger. One method on this interface could define the environment variables that a debugger reads, another method could be used to deduce the pid. Otherwise it is difficult to track what information is used by each debugger (For example, the getEnv function currently has go and java specific content. This is something we seek to avoid through our debugger interfaces.)
• I think this feature merits some unit tests that shows how various JAVA_TOOL_OPTIONS values are parsed into debug ports and how multiple debug port specifications are distilled to a single target port.