vote: add ephemeral bankhash and slot to TowerSync

[AshwinSekar]

Problem

Asynchronous execution needs to track the ephemeral bank hash separately from the latest replayed bank hash. Additionally we need a slot # to now go with the bank hash. This requires a new vote ix format.

Summary of Changes

Since we are already in the midst of a vote ix upgrade for block_id, add this now to avoid having to go through another migration.

[mergify]

The Firedancer team maintains a line-for-line reimplementation of the
native programs, and until native programs are moved to BPF, those
implementations must exactly match their Agave counterparts.
If this PR represents a change to a native program implementation (not
tests), please include a reviewer from the Firedancer team. And please
keep refactors to a minimum.

[AshwinSekar]

feature is rekeyed to avoid any accidental activation before this is released

[wen-coding]

Thanks for adding this!

[lheeger-jump]

Should we collab on the SIMD first before getting too dug in on implementation details?

[AshwinSekar]

Should we collab on the SIMD first before getting too dug in on implementation details?

I'm fine with this, I suggested this change because we're already adding a new vote ix for block_id so figured it would be easier to have 1 migration rather than 2.

However it seems like we're not in a rush for block_id so happy to wait until we've agreed on the APE SIMD first.

[wen-coding]

Should we collab on the SIMD first before getting too dug in on implementation details?

Sure, still working on the SIMD, but comments welcome: solana-foundation/solana-improvement-documents#165