* Fix fungible unbalanced trait

* Add simple decrease_balance test

Signed-off-by: Oliver Tale-Yazdi <[email protected]>

* Fix decrease_balance_at_most

* Fix decrease_balance_at_most in fungibles

* Rename free_balanceto balance_on_free

* Use reducible_balance instead of balance_on_free

Signed-off-by: Oliver Tale-Yazdi <[email protected]>
Co-authored-by: Oliver Tale-Yazdi <[email protected]>