add new extrinsic for removing stableswap liquidity from omnipool lp/omnipool lp in farm

[DuriSK]

It would be great to have extrinsic(s) which will calculate for UI necessary balances when removing stableswap shares from either omnipool position or omnipool farming position.
This is currently handled in 3 signing steps.

Revert OmnipoolLiquidityMining.addLiquidityStableswapOmnipoolAndJoinFarms
depositId
list of farms (because you can be in multiple farms)

Omnipool liquidity (in farm)=>omnipoolLiquidityMining.withdrawShares(args)=>Omnipool LP position(not in farm)=>omnipool.removeLiquidityWithLimit(args)=>stableswap shares=>remove proportionally/single asset=> assets

example of proportional liquidity removal (from stableswap)l:

{
"args": {
"pool_id": "102",
"share_amount": "9,868,770,921,034,374,665",
"min_amounts_out": [
{
"assetId": "10",
"amount": "4,917,091"
},
{
"assetId": "22",
"amount": "4,983,877"
}
]
},
"method": "removeLiquidity",
"section": "stableswap"
}

example of single side removal(from stableswap):

{
"args": {
"pool_id": "102",
"asset_id": "22",
"share_amount": "9,868,770,921,034,374,665",
"min_amount_out": "9,898,643"
},
"method": "removeLiquidityOneAsset",
"section": "stableswap"
}

1. omnipool position in farm => omnipool position (not in farm)=>stableswap shares=>asset
2. omnipool position (not in farm)=>stableswap shares=>asset

2 options how to withdaw shares from stablepool :

• proportionally
• single asset