Unit test for `extendBlock` on historical mainnet blocks

[rootulp]

Context

https://github.com/celestiaorg/celestia-node/pull/4219/files#r2046888052

Proposal

It would increase confidence if celestia-node had a test for extendBlock that used block data from historical mainnet blocks. This data can be saved in testdata/ and then extendBlock can be invoked on them to verify that the generated EDS data root matches what was produced on mainnet for that block. It is worth including a few sample blocks that span app versions (v1, v2, v3) and span a few different types of tx data (regular blobs, authored blobs, empty block).

[SaveTheAles]

Is it still relevant?

[rootulp]

Yes.

[moldis]

on behave of @SaveTheAles (Noders team), I am gonna pick up this issue @rootulp