- Separate converted parameter rules from ParamFlowManager. Now the converted rules will be kept in GatewayRuleManager directly.
- Add a GatewayFlowSlot to do separate flow checking for generated rules.
- Refactor rule converting mechanism: now gateway rules in normal mode (without parameter) will also be converted to a parameter flow rule. The index will be the last (the last position). In GatewayParamParser we put a constant value to the last position.

Signed-off-by: Eric Zhao <sczyh16@gmail.com>