Create mainnet genesis in code

[gjermundgaraba]

Create a new command or something that creates a realistic mainnet genesis (to the extent we know right now).

Context: to keep automated and manual testing of the real genesis consistent + we can develop our genesis file creation directly in code and therefore have nice versioning.

Osmosis seems to have done something a bit similar: https://github.com/osmosis-labs/osmosis/blob/main/cmd/osmosisd/cmd/genesis.go

Tasks

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1. Create a reusable function that returns the genesis (in a form that can be modified, for tests and stuff)
2. Create a (cli) command for creating the genesis file
3. Change tests to start using the new genesis as a basis
4. Prepare genesis module params

[ba1ciu]

Reopening as we till have to decide on mainnet module params.