Possible problems with TDX attestation and the ability to change TSS account ID / endpoint

[ameba23]

#1051 introduces storing provisioning certification keys (PCKs), used for on-chain attestation the the TS server is running in a trusted domain.

The PCK is tied to the physical hardware the server runs on, so if a TS server moves, the PCK will need to change.

Since we have extrinsics which allow validators to change their associated TSS account ID and IP address, we need to allow them to also change their PCK. There are a few things to think about when implementing this:

• If an endpoint (IP address) changes, probably the PCK must also change, so maybe this should be enforced by having a single extrinsic to update both of them.
• When the PCK is changed, the same process of validating the PCK certificate must be carried out as when the validator joins initially. This part is not yet implemented.

[ameba23]

Related to #982

[ameba23]

Linking to another related issue: #1072