Staking / unstaking SLP into SDL/ETH gauge

[hammeiam]

We would like to display and promote the SDL/WETH Sushi pool in our UI. We do not currently have a way to natively interact with non-saddle pools, so this will be some custom logic. Here are the requirements:

• The UI should look mostly like a regular pool, but without the Volume
• Should only be displayed on mainnet, only when IS_VESDL_LIVE is true
• Should always be the first pool shown
• Should have a place to show the user's staked balance (I believe our existing pools already have UI for this)
• When the user clicks "stake" or "unstake", UI should appear that shows the user's stakeable balance, collects their input, and has a button to initiate a transaction. See https://app.alchemix.fi/farms as an example. This should probably reuse our TokenInput component if possible.
• We only need the UI for this ticket, I can add the contract logic shortly.
• It would be nice to somehow differentiate it from the normal Saddle pools, but we can figure this out later.

I'm open to any other ideas to make this component more usable - I trust your judgement.

[hammeiam]

Note, I have a PR up which exposes the Sushi Contract. This PR will automatically fetch the user's sushi lp token balance and make it available via the UserStateProvider. The pool's totalSupply will be available in redux. https://github.com/saddle-finance/saddle-frontend/pull/1099

In another PR, I will account for the sushi pool in gauges and gauge aprs.