[SDK] Get merkle trees and proofs from API instead of IPFS

[bitbeckers]

• Update getMerkleTreeFromIPFS to a method that first tries to query from the DB. (probably to something like getAllowlistForHypercertId(...)
• Update getProofsFromAllowlist to use the new or updated method

[bitbeckers]

First implement in SDK, then use that method in the Indexer