Provide a MockDA for tests

[Ferret-san]

Certain tests, like calldata_source_test.go require a DAConfig in order to work, but without a MockDA, the tests are likely to fail whenever DataFromEVMTransactions is called, thus a MockDA or key-value store of sorts would help us in having proper testing

[nuke-web3]

Think https://github.com/celestiaorg/localestia is the best way to solve for that in the future?

Closing as we are archiving this repo, see #544 .
If still relevant, please do comment and/or re-open so we can triage it together!