Add `crypto.ecrecover` for ethereum signature verification

[ziegfried]

Feature request

There is currently no (easy) way to verify a signature that was created via Ethereum's eth_sign.

Please add the means to verify the elliptic curve signature created in a dapp or an ethereum smart contract. Ideally add a crypto.ecrecover function (or similar) to the graph-ts API.

This would be useful when processing data from dapps like Peepeth, where user-signed actions are stored in IPFS in batches.

While it should be possible to build this assemblyscript, it's likely a lot of work 😇and possibly not as efficient compared to a host export.

[Jannis]

It looks like we could depend on https://github.com/ewasm/ewasm-precompiles/blob/36dce2e652cc0687bbd5ecff7d74c7e39e8fb914/ecrecover/src/lib.rs#L20 to provide this method.

[hbriese]

Any progress on this? ecrecover is pretty essential