Rotate roots per spec

[hosseinsia]

Update root following the TUF specification v1.0.19
https://theupdateframework.github.io/specification/v1.0.19/index.html#load-trusted-root

Logic:

1. Call the update root first in any client updates.
2. Start from the current root version (n), loop through next versions by trying to fetch (n+1).root.json file.
3. For any new root, verify the signatures.