Determine whether Python source files that import Scapy can be licensed Apache 2.0, or must be GPL 2

[jafingerhut]

Scapy is released under GPL 2 license, NOT the Lesser GPL 2. It is not yet clear to me whether this means that Python programs that import Scapy must also be GPL 2. Find out the answer and document it somewhere for all p4lang projects to follow the same practice as each other.

• Scapy license: https://github.com/secdev/scapy/blob/master/LICENSE
• GNU General Public License, Version 2: https://www.gnu.org/licenses/old-licenses/gpl-2.0.en.html

[jafingerhut]

If the P4 Technical Steering Team or P4 Governance Board give instructions to do otherwise, I will change this later, but for now I have changed the SPDX-License-Identifier line of all Python source files that import the Scapy package to say they are GPL-2.0-only, here: #665