Make the core logic deal with tok instead of tez

[gkaracha]

Though this transition is pretty menial, it is a necessary first step for addressing #213, independently of the path we end up choosing (conditional compilation vs. having a tez/FA2 wrapper contract). By making all the core logic deal with an opaque-ish type tok we can defer the choice of collateral type to a higher level. With this PR checker.ml deals with tez—as it did before—and makes calls to tok_of_tez before calling core logic and tez_of_tok when interpreting results from core logic. No other module makes calls to these conversion functions (excluding the tests ofc).

While working on this I also noticed that our API uses tez in names which we probably want to rename to something more generic: Deposit_tez and Withdraw_tez (which I think we could rename to Deposit_collateral and Withdraw_collateral).

[github-actions]

Gas costs	760cab0	6e0b6d8	Diff
create_burrow	47817	48914	1097
touch	537877	538751	874
activate_burrow	53700	54538	838
deposit_tez	53015	53731	716
withdraw_tez	57567	58280	713
deactivate_burrow	59027	59284	257
mint_kit	52111	51865	-246
remove_liquidity	73790	73899	109
add_liquidity	73538	73647	109
buy_kit	69524	69633	109
sell_kit	68651	68760	109

Entrypoint sizes	760cab0	6e0b6d8	Diff
create_burrow	909	1097	188
activate_burrow	1147	1292	145
touch	56479	56614	135
deposit_tez	1041	1163	122
withdraw_tez	1376	1488	112
liquidation_auction_claim_win	978	1062	84
mint_kit	1637	1588	-49
touch_liquidation_slices	14471	14508	37
deactivate_burrow	1568	1603	35
mark_for_liquidation	17127	17093	-34
add_liquidity	1942	1967	25
buy_kit	1351	1376	25
remove_liquidity	2013	2038	25
sell_kit	1347	1372	25
liquidation_auction_place_bid	2229	2213	-16
cancel_liquidation_slice	12185	12177	-8

Test coverage	760cab0	6e0b6d8	Diff
tok.ml	None	97.37	97.37
liquidationAuction.ml	78.14	77.83	-0.3100000000000023
burrow.ml	96.54	96.26	-0.28000000000000114
checker.ml	89.94	90.08	0.14000000000000057
TOTAL	93.93	93.96	0.029999999999986926

[github-actions]

Gas costs	5a87e8a	dab3ff6	Diff
create_burrow	47817	48914	1097
touch	537877	538751	874
activate_burrow	53700	54538	838
deposit_tez	53015	53731	716
withdraw_tez	57567	58280	713
deactivate_burrow	59027	59284	257
mint_kit	52111	51865	-246
remove_liquidity	73790	73899	109
add_liquidity	73538	73647	109
buy_kit	69524	69633	109
sell_kit	68651	68760	109

Entrypoint sizes	5a87e8a	dab3ff6	Diff
create_burrow	909	1097	188
activate_burrow	1147	1292	145
touch	56479	56614	135
deposit_tez	1041	1163	122
withdraw_tez	1376	1488	112
liquidation_auction_claim_win	978	1062	84
mint_kit	1637	1588	-49
touch_liquidation_slices	14471	14508	37
deactivate_burrow	1568	1603	35
mark_for_liquidation	17127	17093	-34
add_liquidity	1942	1967	25
buy_kit	1351	1376	25
remove_liquidity	2013	2038	25
sell_kit	1347	1372	25
liquidation_auction_place_bid	2229	2213	-16
cancel_liquidation_slice	12185	12177	-8

Test coverage	5a87e8a	dab3ff6	Diff
tok.ml	None	97.37	97.37
liquidationAuction.ml	78.14	77.83	-0.3100000000000023
burrow.ml	96.54	96.26	-0.28000000000000114
checker.ml	89.94	90.08	0.14000000000000057
TOTAL	93.93	93.96	0.029999999999986926

[utdemir]

LGTM :). I fixed a trivial issue and rebased, so if you want to make changes you might need a hard reset.

[gkaracha]

LGTM :). I fixed a trivial issue and rebased, so if you want to make changes you might need a hard reset.

Thanks for having a look! 🙏 No more changes I think, this PR is large enough as it is; I'll go ahead and merge it 🙂