MFH: r448354

devel/py-extras: Fix Python 3.x packaging

Python 3.x changes the location of the compiled python objects - pyc and pyo.
The pkg-plist supplied with devel/py-extras doe not account for this, so
packaging with Python 3 fails.

This change replaces pkg-plist with autoplist to correct the issue [1]

While I'm here:

• Add TEST_DEPENDS and test target
• Mark architecture independence
• Add LICENSE_FILE

PR: 219278
Submitted by: Johannes Jost Meixner [1]
Approved by: portmgr (blanket)

Approved by: ports-secteam (blanket)