exchanges/futures: Implement open interest (#1417)

* adds open interest to exchanges

* ADDS TESTING YEAH

* New endpoints, BTSE, RPCS, cached

* slight design change, begin gateio

You will need to get cached for
each exchange that supports it

* gateio, huobi, rpc

* fix up kraken, cache retrieval

* okx, gateio

* finalising all implementations and tests

* definitely my final ever commit on this

* Well, well, well

* final v2

* quick fix of bug

* test coverage, assert notempty, test helper

Added a new testhelper for currency
management because its very annoying
in a parallel test setting which wastes
so much space otherwise

* minimises REST requests for Open Interest

* types.Number merge misses

* Minimises Kraken REST calls

* len change, value -> pointer receiver

* further fixup

* fixes gateio, batch calculates open interest

* single gateio, lint const fixes

* rejig and more thorough oi for huobi

* formatting expansion

* minor fix for handling expiring contracts

* rm unused Binance strings

* add bybit support, fix bybit issues

* oopsie doopsie, dont look at my whoopsie

* Fix issue, remove feature

* move an irrelevant function for the pr

* mini bybit upgrades

* fixes cli request bug

testdata/http_mock/binance/binance.json

@@ -263323,10 +263323,10 @@
     {
      "data": {
       "contractType": "PERPETUAL",
-      "openInterest": "1603856",
+      "openInterest": "6784657",
       "pair": "BTCUSD",
       "symbol": "BTCUSD_PERP",
-      "time": 1607293625325
+      "time": 1702244982986
      },
      "queryString": "symbol=BTCUSD_PERP",
      "bodyParams": "",
@@ -325935,9 +325935,9 @@
    "GET": [
     {
      "data": {
-      "openInterest": "37679.027",
+      "openInterest": "83782.317",
       "symbol": "BTCUSDT",
-      "time": 1602819815902
+      "time": 1702244985273
      },
      "queryString": "symbol=BTCUSDT",
      "bodyParams": "",