Move evidence from data square back to Tendermint block

[rootulp]

Context

During the QGB Slashing design finalization meeting, we decided to remove evidence from the data square back to the Tendermint block. This likely involves changes in pkg/shares and celestia-core

Tasks

• Move evidence back to Tendermint block celestia-core#894
• Remove evidence from pkg/shares #1068

[rootulp]

https://github.com/celestiaorg/celestia-core/blob/9002f1bf6be303d2a6f46865ead288812fc9a49a/types/block.go#L1014 makes me think that Evidence was never actually removed from the Tendermint block. @liamsi are you aware of commits or modifications in celestia-core that need to be reverted?

[liamsi]

@liamsi are you aware of commits or modifications in celestia-core that need to be reverted?

This is the change in question: celestiaorg/celestia-core#19

Particularly, block.go:
https://github.com/celestiaorg/celestia-core/pull/19/files#diff-77409c5f41482f194140901cdad16d5bf6e5e6b3591f275dbf3660f12615078c

This might look like this it does not matter where that field is but in fact only block.Data gets erasure coded and can sampled. Also, the evidence is currently part of the data root.

Before we revert this though, we should capture the rationale of WHY we would want to revert this. As @musalbas said, we should park this for a bit before acting on it.

[rootulp]

The rationale for reverting is:

1. to minimize the diff between celestia-core and tendermint
2. because we don't expect to have state fraud proofs on mainnet in the immediate future and evidence in the data square only becomes desirable after we have state fraud proofs

[evan-forbes]

removed the epic tag for now, as this can be accomplished with 1 PR in core, and a PR here to update/delete code in the shares package. pls feel free to change if we think other wise.

[rootulp]

Done via celestiaorg/celestia-core#894 and #1068