See also #32165
In old `GetResourceGroupByCollection` implementation, it iterates all
replicas to match collection id, which is slow and CPU time consuming.
This PR make it utilize the coll2Replicas mapping by calling
`GetByCollection` and mapping replicas into resource group.
Signed-off-by: Congqi Xia <congqi.xia@zilliz.com>
Signed-off-by: Congqi Xia <congqi.xia@zilliz.com>