refactor: remove epochs

[puneet2019]

closes #447
closes #457

[github-actions]

Coverage after merging puneet/remove-epochs into main

61.13%

Coverage Report

File	Branches	Funcs	Lines	Uncovered Lines
simapp
encoding.go	100%	100%	100%
test_suite.go	100%	100%	0%	..., 37, 38, 39, 41
genesis_account.go	100%	100%	100%
test_helpers.go	100%	100%	18.14%	..., 51, 52, 98, 99
export.go	100%	100%	14.18%	..., 96, 97, 98, 99
genesis.go	100%	100%	0%	19, 20, 21
app.go	100%	100%	84.22%	..., 824, 825, 826, 827
simapp/params
proto.go	100%	100%	100%
simapp/simd
main.go	100%	100%	0%	..., 21, 22, 23, 24
simapp/simd/cmd
genaccounts.go	100%	100%	70.45%	..., 95, 97, 98, 99
root.go	100%	100%	80.89%	..., 68, 71, 72, 91
x/halving
module.go	100%	100%	73.13%	..., 70, 74, 75, 76
autocli.go	100%	100%	100%
genesis.go	100%	100%	77.78%	16, 24
abci.go	100%	100%	15.38%	..., 49, 50, 51, 52
x/halving/client/cli
tx.go	100%	100%	54.76%	..., 59, 60, 61, 63
x/halving/keeper
grpc_query.go	100%	100%	0%	..., 21, 22, 23, 25
msg_server.go	100%	100%	30%	..., 34, 35, 36, 38
keeper.go	100%	100%	48.89%	..., 90, 94, 95, 96
x/halving/simulation
genesis.go	100%	100%	70%	17, 18, 19
x/halving/types
codec.go	100%	100%	53.33%	..., 44, 45, 46, 47
msg.go	100%	100%	0%	..., 53, 54, 55, 57
params.go	100%	100%	85.29%	23, 24, 25, 43, 44
genesis.go	100%	100%	86.67%	25, 26
x/lsm/distribution
codec.go	100%	100%	100%
x/lsm/staking
codec.go	100%	100%	100%
x/pob/types
msgs.go	100%	100%	0%	..., 37, 40, 41, 42
codec.go	100%	100%	0%	..., 40, 41, 42, 43