chore: Use either viem or ethers v6

[rackstar]

Overview

Current the SDK is using both libraries. We should just pick one.

We should also check what clients use of the 2 as it might make integration with the SDK easier if we use the same lib.

[Gideonnn]

We only use ethers in build scripts and test files, so I made a pr moving it from dependencies to devDependencies. This has no effect on the bundle size, but only on the node_modules folder of consuming projects (it doesnt install ethers anymore).

I tried fetching events with viem but it resulted in an empty array everytime. By reading the docs I could not figure out what was causing this. I left some code examples in the pr, for when we decide to pick this up again. Check out pr #140