Updates for 2024 jan 01 (#662)

* Move optional steps for testing VMs out of README.md file
This may help avoid new users being confused that they must follow
those instructions.

Signed-off-by: Andy Fingerhut <andy_fingerhut@alum.wustl.edu>

* Updates to P4 source repo versions for 2025-Jan-01

Signed-off-by: Andy Fingerhut <andy_fingerhut@alum.wustl.edu>

---------

Signed-off-by: Andy Fingerhut <andy_fingerhut@alum.wustl.edu>

Author: jafingerhut

vm-ubuntu-24.04/install.sh

@@ -23,10 +23,10 @@ THIS_SCRIPT_DIR_ABSOLUTE=`readlink -f "${THIS_SCRIPT_DIR_MAYBE_RELATIVE}"`
 
 ${THIS_SCRIPT_DIR_ABSOLUTE}/user-bootstrap.sh
 
-# 2024-Dec-01 versions:
-export INSTALL_BEHAVIORAL_MODEL_SOURCE_VERSION="005c6cf0f9bb40bfa89d3ca4066ab22f09975d9a"
+# 2025-Jan-01 versions:
+export INSTALL_BEHAVIORAL_MODEL_SOURCE_VERSION="7ca39eda3529347e4ba66f1976351b0087294bf8"
 export INSTALL_PI_SOURCE_VERSION="2bb40f7ab800b91b26f3aed174bbbfc739a37ffa"
-export INSTALL_P4C_SOURCE_VERSION="df9e3ee28ae9b1d9d370c7b8543a953a1c490bc3"
+export INSTALL_P4C_SOURCE_VERSION="1dc0afae2207f4bb9f5ab45f105ed569cc1ac89b"
 export INSTALL_PTF_SOURCE_VERSION="c554f83685186be4cfa9387eb5d6d700d2bbd7c0"
 
 ${THIS_SCRIPT_DIR_ABSOLUTE}/install-p4dev-v8.sh