Mexc fetchTime : handleMarketTypeAndParams
Mexc fetchTime : handleMarketTypeAndParams

Adjusted handleMarketTypeAndParams to be one line so that it's cleaner in php and python. Added margin market type:
```
2022-01-20T03:06:37.387Z
Node.js: v16.9.1
CCXT v1.67.58
mexc.fetchTime ()
314 ms
1642647998933
```

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