refactor: simplify swap fee update workflow

[chefburger]

Changes:

1. rename src/libraries/FeeLibrary.sol to src/libraries/SwapFeeLibrary.sol so that it makes more sense and avoid mixup with protocolFee (Fee.sol)
2. This PR switched up how we update swap fees from pulling to pushing, hence instead of

1. someone call `updateDynamicSwapFee()` on poolManager to trigger update
2. poolManager fetch the fee through `hook.getFee(msg.sender, key);`

we do

hook call `updateDynamicSwapFee(poolKey, newDynamicFee)` directly

Potential update for third party hooks:

For dynamic fee pool, the initial swap fee is 0 and must be set in afterInitialize hook if a nonzero value is expected

[ChefMist]

(optional) then the swap fee is controlled by hook -> then the swap fee can be updated by hook

[ChefMist]

will keep a note to update developer docs and hooks-template probably to reflect new dynamic fee model (push)