Bug: rounding invariant failures in `kickWithDeposit` and `removeQuoteToken`

[grandizzy]

Description of change

High level

• Kick with deposit reverts due to rounding: calculated unscaled amount to remove from deposit (for amount to debit from deposit to cover bond) could be bigger than actual unscaled amount of deposit (since ceilWdiv is used). This results in tx reverting and kick with deposit failure
  • Fixed by using floorWdiv and adding extra check for remove amount to be the min of calculated amount and deposit amount. Used floorWmul to round down scaled amount
  • Applied same fix for remove quote token: round down when calculate scaled amount and round up ( ceilWdiv) unscaled amount to remove. Check the unscaled amount to remove from deposit to not exceed amount in deposit
  • Added similar protection (make sure amount to remove does not exceed deposit amount) for remove on bucket take
  • Invariants changes:
  • set F1 and F2 deviation back to 1e12 (were changed to quote token scale but this lowers deviation to 1 in case of 18 decimals)
  • use ceilMul when computing amount for F3 (since Fenwick change to allow higher debt but lower precision https://github.com/ajna-finance/contracts/pull/857)
  • bump reserves invariant deviation to 1e13, inline with QT1 invariant deviation

Contract size

Pre Change

  TakerActions             -  15,104B  (61.46%)
  LenderActions            -  10,581B  (43.05%)
  KickerActions            -  10,435B  (42.46%)

Post Change

  TakerActions             -  15,129B  (61.56%)
  LenderActions            -  10,637B  (43.28%)
  KickerActions            -  10,427B  (42.43%)

Gas usage

Pre Change

| Function Name                        | min             | avg    | median | max     | # calls |
| addQuoteToken                        | 122500          | 179775 | 164363 | 817387  | 60004   |
| bucketTake                           | 309224          | 327865 | 327866 | 346507  | 4       |
| drawDebt                             | 253215          | 298204 | 272111 | 812414  | 136003  |
| kick                                 | 149467          | 223488 | 221980 | 1034805 | 48000   |
| kickWithDeposit                      | 199746          | 277377 | 273523 | 1000731 | 8000    |
| moveQuoteToken                       | 290958          | 290958 | 290958 | 290958  | 1       |
| removeQuoteToken                     | 147296          | 171440 | 176084 | 195785  | 4000    |
| repayDebt                            | 576921          | 609077 | 598969 | 757339  | 16002   |
| settle                               | 350544          | 350544 | 350544 | 350544  | 1       |
| take                                 | 81772           | 83349  | 83084  | 315391  | 15998   |

Post Change

| Function Name                        | min             | avg    | median | max     | # calls |
| addQuoteToken                        | 122497          | 179771 | 164360 | 715160  | 60004   |
| bucketTake                           | 309308          | 327949 | 327950 | 346591  | 4       
| drawDebt                             | 253002          | 297991 | 271898 | 812201  | 136003  |
| kick                                 | 149467          | 223488 | 221980 | 1034805 | 48000   |
| kickWithDeposit                      | 199539          | 277170 | 273316 | 1000524 | 8000    |
| moveQuoteToken                       | 270637          | 270637 | 270637 | 270637  | 1       |
| removeQuoteToken                     | 147259          | 171411 | 176047 | 198212  | 4000    |
| repayDebt                            | 576921          | 609077 | 598969 | 757339  | 16002   |
| settle                               | 350544          | 350544 | 350544 | 350544  | 1       |
| take                                 | 81772           | 83349  | 83084  | 315391  | 15998   |

[grandizzy]

retiring in favor of https://github.com/ajna-finance/contracts/pull/869 will address comments in there