[Feature] Add user property to limit the instance num

[liutang123]

Is your feature request related to a problem? Please describe.
In a multi-user cluster, some users often submit some very unreasonable queries. These queries often use a lot of resources, making other users unable to query.

Describe the solution you'd like
Add a max_query_instances user property to limit the number of instances a user can use.

Describe alternatives you've considered
Use more accurate query load scores instead of simple instances.

Additional context