Process events in Aztec.nr

[benesjan]

Similarly to how we process notes in Aztec.nr we should process events as well.

This will most likely require us to significantly change the flow because currently we decrypt events only when requested (we have block num on the API input, then we fetch the block, decrypt the events and apply filters).

With the change to Aztec.nr we will most likely want to decrypt the events as they come and store them in a PXE db decrypted and unpacked.