Support aggregation in validator

[Riateche]

• Change dependency versions to make the crate compatible with pythnet validator
• Add flags to price account to track transition from v1 to v2
• Implement transition between v1 and v2 by calling add_publisher with a special pubkey
• Skip aggregation and message buffer update in the oracle program if v2 aggregation is enabled
• Clear message buffers after transition to v2
• Expose aggregation as a library function to be used in the validator

[jayantk]

left a few minor comments and one maybe significant question -- see inline

[ali-bahjati]

I think as Jayant said, would be nice to test the validator update code path too.

[guibescos]

I think there might be an edgecase where the price stops aggregating (both v1 and v2).
In a given slot:

• upd_price : aggregation is unsuccessful therefore message_sent_ == 1
• flags gets activated
• aggregation v2 fails with V1AggregationMode since PriceAccountFlags::MESSAGE_BUFFER_CLEARED is false

Next slot:

• upd_price no longer triggers an aggregation because PriceAccountFlags::ACCUMULATOR_V2 is true
• aggregation v2 also fails since PriceAccountFlags::MESSAGE_BUFFER_CLEARED is false

And so on...
let me know if you agree

[Riateche]

I think there might be an edgecase where the price stops aggregating (both v1 and v2).

Good catch! I've changed the code so that the MESSAGE_BUFFER_CLEARED is set regardless of the message_sent_ flag. I think this should fix the issue.

[ali-bahjati]

nit: can we once verify the output of this as well?

[Riateche]

Added some output checks.

[ali-bahjati]

LGTM!

[jayantk]

this comment seems like it doesn't apply to anything

[Riateche]

Looks like it's no longer relevant. Removed.