issue: #38142
pr: #38143
current balance channel policy only consider current collection's
distribution, so if all collections has 1 channel, and all channels has
been loaded on same querynode, after querynode num increase, balance
channel won't be triggered.
This PR enable score based balance channel policy, to achieve:
1. distribute all channels evenly across multiple querynodes
2. distribute each collection's channel evenly across multiple
querynodes.
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Signed-off-by: Wei Liu <wei.liu@zilliz.com>
83e162f5f1