Add option to specify slippage limit to addLiquidityStableswapOmnipoolAndJoinFarms wrapper

[DuriSK]

Comparing this function to addLiquidityAndJoinFarms it would be useful if it would be possible to add slippage (min amoun) limit also to this stableswap function.
Add min_shares_limit

[dmoka]

	pub fn add_liquidity_stableswap_omnipool_and_join_farms(
		origin: OriginFor<T>,
		stable_pool_id: T::AssetId,
		stable_asset_amounts: BoundedVec<AssetAmount<T::AssetId>, ConstU32<MAX_ASSETS_IN_POOL>>,
		farm_entries: Option<BoundedVec<(GlobalFarmId, YieldFarmId), T::MaxFarmEntriesPerDeposit>>,
		min_shares_limit: Option<Balance>,
	)