Support for configurable network address for user-v2

[balajiv113]

Description

Not configurable as of now. I will provide this support in a follow-up PR.
This needs some changes related to DNS resolving as well

Originally posted by @balajiv113 in #1383 (comment)

[balajiv113]

Changes are almost ready for this as well.

Mostly waiting for containers/gvisor-tap-vsock#217 to be merged.