[sled-agent] Delete OPTE state on sled-agent startup

[bnaecker]

Currently at sled agent startup, we're deleting any existing VNICs that follow a particular naming convention. This is temporary, but the goal is for the sled agent to ensure the system is in a known-good state before proceeding. (See this issue for related discussion, especially how to recover the state rather than delete in the future).

This issue tracks adding a similar set of steps for cleaning up and state related to OPTE or the xde driver. This includes:

• Deleting the VNICs on top of any xde devices
• Deleting the xde devices themselves

[bnaecker]

Closed by #1052