Make roconfig depend on chain

[domob1812]

We should allow the roconfig data to depend on the chain the game is running on. In particular, for regtest it should merge in the test item types, but keep them out for mainnet and testnet. It could just be another instance that gets merged in (with additional types and parameter overrides) on regtest.

When this is done, we can also use it to migrate some (or maybe all?) of Params to values in the roconfig proto instead.