Collateral updater component

[Niederb]

For the on-chain verification we need collateral information (provided by the Intel PCCS) and so we need a component that can do this on somewhat regular intervals. I see multiple options:

• The worker can always do this on startup before sending the actual quote

  • Leads to sending a lot of duplicate information to the chain
  • How quickly can the pallet can decide that the collateral is already available?
  • We could even think about not storing the collateral on-chain at all but then we need to verify the collateral every time we register an enclave
    • Probably too much overhead

• The worker could do it if it gets some kind of 'MISSING_COLLATERAL_ERROR`

  • Additional logic in the worker

• There could be an independent component (inside the worker?) that does this

  • I don't think the PCCS has an API that allows to get events when the collateral data has changed
  • One way could be to check the date of the sqlite database
    • Not all PCCS setups use sqlite
    • How reliable is this? Many false positive notifications?
    • Component needs to be on the same machine as the PCCS

• An interesting question: Can we generate an enclave quote without Intel PCCS? I think in theory this should be possible, but I'm not sure if the Intel API actually supports this.