LimitOrderHook improvements

[NoahZinsmeister]

Infra improvements

• way more tests

Contract improvements

• consider simplifying the epoch/key data structures (https://github.com/Uniswap/core-next/pull/93#discussion_r888166349)
• consider renaming epochs -> orders (https://github.com/Uniswap/core-next/pull/93#discussion_r889726019)
• consider a bitmap to track initialized ticks (https://github.com/Uniswap/core-next/pull/93#discussion_r889730737)
• consider a single call to fill per swap (https://github.com/Uniswap/core-next/pull/93#discussion_r889739044)

UX-level changes

• consider taking amountIn instead of liquidity (https://github.com/Uniswap/core-next/pull/93#discussion_r888143083)
• consider issuing erc721/erc1155/erc20 representations of limit orders

[willpote]

Should it be possible to place a limit order within a range that the price is currently in?

Can you withdraw a partially filled order?

Confirm that partially filled but subsequently unfilled orders remain fully unfilled from an accounting perspective.