Router: add a liquidity endpoint (draft)

[farnyser]

Fetch total liquidity (in US $) of a token reachable through autobahn

This first version compute an estimation of reachable liquidity using existing quoting API and an heuristic (if output stop to grow with input, then it means we reached max available quantity for a pool)
It could be improved by using dex specific code.

Query example (for SOL, USDC, MNGO & WIF):

http://127.0.0.1:8888/liquidity?mints=So11111111111111111111111111111111111111112,EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v,MangoCzJ36AjZyKwVj3VnYU4GTonjfVEnJmvvWaxLac,EKpQGSJtjMFqKZ9KQanSqYXRcF8fBopzLHYxdM65zcjm

Result:

{
  "liquidity": {
    "EKpQGSJtjMFqKZ9KQanSqYXRcF8fBopzLHYxdM65zcjm": 1651150.4687013852,
    "EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v": 15627441.321525,
    "MangoCzJ36AjZyKwVj3VnYU4GTonjfVEnJmvvWaxLac": 173.31381035204276,
    "So11111111111111111111111111111111111111112": 44315126.80003761
  }
}