feat!: introduce InfoReservedBytes

[rootulp]

Description

BREAKING CHANGE: MsgShareSize is now one byte smaller. This change will break clients who parse msg shares (ex. celestia-app)

Part of #839

[rootulp]

CI failed on:

--- FAIL: TestTxInclusion (2.11s)
panic: input length must be a multiple of 64 [recovered]
	panic: input length must be a multiple of 64

Fixing this involves adding Info to the Message struct

type Message struct {
	// NamespaceID defines the namespace of this message, i.e. the
	// namespace it will use in the namespaced Merkle tree.
	//
	// TODO: spec out constrains and
	// introduce dedicated type instead of just []byte
	NamespaceID namespace.ID

	// Info is a byte with the following structure: the first 7 bits are
	// reserved for version information in big endian form (initially
	// `0000000`). The last bit is a "message start indicator", that is `1` if
	// the share is at the start of a message and `0` otherwise.
	Info byte

	// Data is the actual data contained in the message
	// (e.g. a block of a virtual sidechain).
	Data []byte
}

and then updating usage of Message, e.g. in https://github.com/rootulp/celestia-core/blob/27c3aec0b46bb6e7cbfa759c7968659d58161127/types/share_merging.go#L264

However, I'm aware that share_merging.go is being extracted to celestia-app in celestiaorg/celestia-app#637 so I'm not sure how best to proceed without conflicting with the in-flight refactor effort @evan-forbes

UPDATE: synced with Evan and I'll start working off a branch based on celestiaorg/celestia-app#637 and temporarily ignore the errors in celestia-core b/c much of this code will be deleted post move.

[rootulp]

It's possible not all of the changes in this PR are necessary. In particular:

• Put InfoReservedBytes consts in appconsts celestia-app
  • Blocked on Move share constants to celestia-app #841 because https://github.com/celestiaorg/celestia-core/pull/840/files#diff-6572dddc535b4d2c98746d71dde97840af1328797e193db28376939a320be8f8R29
• Replay code changes in this branch on evan/refactor-share-pkg
• Add Version to WireMsgPayForData and MsgPayForData