Refactoring and overhaul of IACFG-generating code.
- joinCFGs: overhauled to simplify using the CallGraph.
- extractCalls: split into enter/exit and calls, using a recursive algorithm and linked lists of nodes.
- Increased project JDK level to 21 (latest LTS).
- Testing: moved
main
tosrc/test/java
andTest.java
tosrc/test/resources
. - Renamed IACFG to ICFG for simplicity.