Refactor/move sync pivot to IBlockTree.

[asdacap]

• Move sync pivot from ISyncConfig into IBlockTree and ancient block barriers so ISyncPointers.
  • Why into IBlockTree? Well, blocktree initialization need it so to prevent adding a new dependency to it, just put it in IBlockTree.
  • Plus if you think of it as FinalizedBlock, which it kinda is, it make a lot more sense.
• Why ancient block barriers into ISyncPointers? Because IBlockTree is a bit fat, and the barriers are more of a sync concern, less important than sync pivot.
  • Combined portal and sharded block, direct era attached storage, the block barriers have a lot of logic.
  • And since ancient barriers rely on sync pivot for some reason, it kinda need to be put outside.

Types of changes

What types of changes does your code introduce?

• Refactoring

Testing

Requires testing

• Yes
• No

If yes, did you write tests?

• Yes
• No

Notes on testing

• Hive sync test passed