Fast-sync disabled with using HC

[PHA-SYSOPS]

IF you configure headerscache once WM starts up it reports 'detected pruned node, disabling fast cache', which is wierd because the node behind it is a full-node. This is likely because of the failover method. I would suggest either allowing this via HC with the node as the backend, or allow a specific fast-sync backend to be configured.

[Nexus2k]

From what I can tell pruntime still doesn't support fast-sync today. https://github.com/search?q=repo%3APhala-Network%2Fphala-blockchain+path%3A%2F%5Estandalone%5C%2Fpruntime%5C%2F%2F+fast&type=code