Allow the ability to provide your own `builtinChainConfigs`

[chatton]

Currently there is a hard coded map of built in chain configs

var builtinChainConfigs = map[string]ibc.ChainConfig{
	"gaia":     cosmos.NewCosmosHeighlinerChainConfig("gaia", "gaiad", "cosmos", "uatom", "0.01uatom", 1.3, "504h", false),
	"osmosis":  cosmos.NewCosmosHeighlinerChainConfig("osmosis", "osmosisd", "osmo", "uosmo", "0.0uosmo", 1.3, "336h", false),
	"juno":     cosmos.NewCosmosHeighlinerChainConfig("juno", "junod", "juno", "ujuno", "0.0025ujuno", 1.3, "672h", false),
	"agoric":   cosmos.NewCosmosHeighlinerChainConfig("agoric", "agd", "agoric", "urun", "0.01urun", 1.3, "672h", true),
	"icad":     cosmos.NewCosmosHeighlinerChainConfig("icad", "icad", "cosmos", "photon", "0.00photon", 1.2, "504h", false),
	"penumbra": penumbra.NewPenumbraChainConfig(),
}

We are able to use NewBuiltinChainFactory which makes creating a ChainFactory very easy, but it would be nice to be able to specify our own defaults, something like

func NewChainFactory(log *zap.Logger, specs []*ChainSpec, builtIns map[string]ibc.ChainConfig) *BuiltinChainFactory

to provide the easy of use and also our set of configs that are specific to our repo and our registries, and maybe don't belong in this particular builtins map.