Set the timeout in milliseconds that the server should wait before returning with a write concern
timeout. This is not the same as a socket timeout. A value of zero may be used to indicate no write
concern timeout.
Beginning in version 1.9.0, this function can now alter the write concern after it has been used in an
operation. Previously, using the struct with an operation would mark it as "frozen" and calling this
function would log a warning instead instead of altering the write concern.
SEEALSO:mongoc_write_concern_get_wtimeout() and mongoc_write_concern_set_wtimeout_int64().