Replace hover::starknet tests

[mkaput]

The hover::starknet family of tests is pretty coarse grained which is neither helpful when it fails, nor it finds precise bugs in our code.

1. Find out what precise code paths of our codebase these tests are testing.
2. Reduce these down to something that is not relying on starknet plugin.
3. Remove hover::starknet tests altogether

Hint: I think all plugin-related stuff in this tests reduces down to #[generate_trait] which is compiler builtin