Implement Liquidity Management APIs

[zbuc]

• Implement a PositionManager, similar to the NoteManager, which will encapsulate all liquidity position-related state management. #1904
• Fill in Position-related ActionHandler implementations #1905
  • PositionOpen
  • PositionClose
  • PositionWithdraw
  • PositionRewardClaim
• Remove existing StubCpmm and direct Swap executions at the DEX engine #1906
• Configure the existing Swap actions to use the new liquidity positions rather than the StubCpmm (should there be a higher level encapsulation here over the liquidity positions, similar to StubCpmm? probably) #1907
• Expose liquidity position management in pcli #1991
• Derive trading function approximation #1908
  • Should estimate the payoff curve of a CPMM using linear positions
  • Propose a desired payoff curve, then generate test positions that approximate that payoff curve
• Minimal smoke test support for position management #1909

Based on details in https://hackmd.io/rsgSwz3BQKuL0GrSF0LWXA# and https://hackmd.io/jtoiMn0pQnSTZlOi2ig5Wg

[conorsch]

Discussed in sync today: we'll get a portion of this week in for 041-adraste (#1877), but the rest of the work will require follow-up tickets.

[conorsch]

Moving to "Future" column in work-planning because this is an epic. For individual subtasks, we'll drag those onto sprint columns going forward.

[hdevalence]

Folding into #1724