Extend `bcc_proc` API. Allow to limit search to specific pid.

[gukoff]

Fixes https://github.com/iovisor/bcc/issues/5013

• Extend bcc_proc API. Allow to limit search to specific pid.
• Also extend the Python binding with the same goal.
• The API changes are backwards-compatible.
• Also added a couple of boundary checks for memcpy

[gukoff]

The failed test seems unrelated to this change; please retry?