[Feature Request]: Migrate to go-square types

[cmwaters]

Implementation ideas

We have a new v2 go square package which is intended to unify the types across both the celestia-node and celestia-app package. As part of preparing to upgrade to v3, we need to migrate the existing core types like:

• Share
• Namespace
• Blob
• BlobTx
• Square

to the new types specified in this repo.

I'm unfamiliar of how this may break the APIs for celestia-node.

V2 of go-square is backwards compatible from the square construction perspective. This means that all squares constructed using the v1 and v2 of the application can be constructed with the v2 go-square. The construction is not forwards compatible. v3 of celestia-app can produce a square (using v2 of go-square) which is different to v1 of go-square.