chore: Add estimate memory usage command for gsctl

[siyuan0322]

Example usage:

❯ PYTHONPATH=`pwd` python3 graphscope/gsctl/gsctl.py estimate -v 222111111 -e 1610000000 -vf 2 -ef 28 -g gae -p 4

Disclaimer: The `estimate` command serves as a estimator for various kind of GraphScope resources.
    - GAE memory usage estimator:
        It would do a rough estimation of the total memory usage of the GAE.
        The actual memory usage may vary vastly due to the complexity of the graph algorithm and the data distribution.

        Here's some assumption when estimating the memory usage:
            1. Assuming the graph is a simple graph, e.g. only has 1 label and at most 1 property for each label.
            2. Assuming the graph algorithms has a fixed amount of memory consumption, e.g. PageRank, SSSP, CC;
               It should not generate a huge amount of intermediate result, like K-Hop, Louvain.
            3. Assuming the vertex map is global vertex map

        User should take this estimation as a reference and a start point for tuning, and adjust the memory allocation according to the actual situation.

[SUCCESS] The estimated memory usage is 30.61 GB per pod for 4 pods.