Unified reader interface for Data Availability providers

[ganeshvanahalli]

This PR introduces a generic reader interface for DA providers to implement.
Multiple implementations can be enabled at once but a batch will only be able to invoke one DA provider (the first occurring valid one in the list).

[Tristan-Wilson]

LGTM

[RISHABHAGRAWALZRA]

Hi, I realised even with the unified read interface, the inbox tracker is still taking it as separate readers https://github.com/OffchainLabs/nitro/blob/master/arbnode/node.go#L532, can't we take it into a single umbrella?

[ganeshvanahalli]

Hi, I realised even with the unified read interface, the inbox tracker is still taking it as separate readers https://github.com/OffchainLabs/nitro/blob/master/arbnode/node.go#L532, can't we take it into a single umbrella?

Hi, we refactored this in 8c256b7 commit of the unified writer interface PR

[RISHABHAGRAWALZRA]

Hi, why do we have a list of the providers here https://github.com/OffchainLabs/nitro/pull/2155/files#diff-e24cacc680b8e01e6610107edccd3114f681d583376a9ffc9614fa87df314b32R66, if I understand correctly, at a time we will be using a single da provider, or am I missed something?