Everywhere including examples, external interop APIs, bindings generators
code and in other valuable places. A couple of `interface{}` usages are
intentionally left in the CHANGELOG.md, documentation and tests.
And test it with the RPC server.
Notice that getters still return int64 instead of *big.Int, that's because
these values are very limited and technically could even fit into an int (but
that seems to be too dangerous to use for long-term compatibility).