## Purpose of the PR
Subtask of #2265.
Adjust the project structure of this repository to include three sub-modules: hugegraph-server, hugegraph-pd, hugegraph-store at the root level.
## Main Changes
Roll back to the moment when https://github.com/apache/incubator-hugegraph/pull/2266 was merged on `pd-store` and incorporate the latest changes in `master`.
For more detailed information, please refer to https://github.com/apache/incubator-hugegraph/pull/2266#issue-1834369489.
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Co-authored-by: M <87920097+msgui@users.noreply.github.com>
M