Prevent bypassing debt ceiling in isolation mode

[matchv]

The issue:

The current debt_ceiling will truncate (asset_decimal - 2) digit when incrementing, it means if the borrow asset is 6 decimals, debt_ceiling will only increment to the precision of 1 cent (10^4).

A user who micro borrows slightly than 1 cent (9,999 unir) each time, for as many times as possible, will bypass the debt ceiling each and every time, which break the protocol integrity.

//validation_logic.move
let isolation_mode_total_debt =
    pool::get_reserve_isolation_mode_total_debt(mode_collateral_reserve_data) as u256;
let total_debt =
    isolation_mode_total_debt
      + (amount
         / math_utils::pow(
             10,
             (reserve_decimals
                - reserve_config::get_debt_ceiling_decimals())
         )
        );
assert!( total_debt <= isolation_mode_debt_ceiling, … );

The fix:

Add ceil_div() in math library
Use ceil_div() to replace simple division in borrow logic, isolation mode, validation logic etc.
Add more test cases

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.89%. Comparing base (566c23b) to head (d4732d0).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #35      +/-   ##
==========================================
- Coverage   97.08%   96.89%   -0.19%     
==========================================
  Files          16       16              
  Lines         514      515       +1     
==========================================
  Hits          499      499              
- Misses         15       16       +1     

Flag	Coverage Δ
move	96.89% <ø> (-0.19%)	⬇️

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[mpsc0x]

I agree with the implementation and the reasoning behind it. LGTM