Fix query timeout

[ptpaterson]

Ticket(s): BT-3938

Problem

• we set x-timeout-ms instead of x-query-timeout-ms
• we send the header as a float, e.g. 5000.0 instead of 5000

Solution

Update the header and header encoding.

Result

Query timeouts are enforced correctly.

Testing

Added a test thatQueryTimeoutErrors get raised when queries run beyond the specified query_timeout configuration.
Added a test for Client.paginate that uses query timeouts to demonstrate that options are getting passed down to requests.

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[ptpaterson]

oops didn't mean to make a draft.