Merge RootCoord, DataCoord And QueryCoord into MixCoord
Make Session into one
issue : https://github.com/milvus-io/milvus/issues/37764
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Signed-off-by: Xianhui.Lin <xianhui.lin@zilliz.com>
Related to #28861
Move allocator interface and implementation into separate package. Also
update some unittest logic.
Signed-off-by: Congqi Xia <congqi.xia@zilliz.com>