Modify the semantic of MP2SP intents introducting the partially failed state

Right now, due to a "ALL or NOTHING" logic implemented in the intent framework, using MP2SP intents, if any end-point (both ingress and egress) fails, the entire intent fails, with a bad impact on the overall user traffic forwarding.

As a user I would like the following behavior, in case something fails:

• If the SINGLE egress point fails all the intent should fails - since the destination is not reachable
• If anything that would prevent all the MP sources to reach the destination fails, the entire intent should fail
• If anything in between a certain source and the destination fails, we should re-route to a sub-optimal path that specific path, without touching the rest of the intent
• If any of the MP sources fails, ONLY that specific part of the intent should fail, causing the overall intent to go in a different state (partially failed?)
• If an intent is partially failed the user should be able to inspect what exactly failed