Remove deprecated API and IJava startup vars

[andrus]

Let's remove support for the previously deprecated IJava APIs and startup variables.

Startup variables

The effect is that the removed will be ignored, and should be replaced with JJava alternatives:

• IJAVA_COMPILER_OPTS -> JJAVA_COMPILER_OPTS
• IJAVA_TIMEOUT -> JJAVA_TIMEOUT
• IJAVA_CLASSPATH -> JJAVA_CLASSPATH
• IJAVA_STARTUP_SCRIPTS_PATH -> JJAVA_STARTUP_SCRIPTS_PATH
• IJAVA_STARTUP_SCRIPT -> JJAVA_STARTUP_SCRIPT

APIs

CodeEvaluatorBuilder.startupScript(InputStream) is gone. There are other ways to load startup scripts.