Correct OKX order amount and price info

[t2o2]

Description of code - what bug does this fix / what feature does this add?

• Change order price from laster order fill price to limit price (limit order) or average fill price (market order)
• Change order amount from last order fill amount to original order size
• Change default remaining amount from 0 to order size
• Fix endpoint on server time acquisition

Order info received after the fix

exchange: OKX symbol: AAVE-USDT-PERP id: 111111 side: buy status: live type: limit price: 100 amount: 1 remaining: 1 account: None timestamp: 1646723193.233
exchange: OKX symbol: AAVE-USDT-PERP id: 111111 side: buy status: live type: market price: 0 amount: 1 remaining: 1 account: None timestamp: 1646723219.467
exchange: OKX symbol: AAVE-USDT-PERP id: 111111 side: buy status: filled type: market price: 118.76 amount: 1 remaining: 0 account: None timestamp: 1646723219.476

• [x] - Tested
• [ ] - Changelog updated
• [x] - Tests run and pass
• [ ] - Flake8 run and all errors/warnings resolved
• [ ] - Contributors file updated (optional)