add compressed graph datacell with Elias-Fano Encoder

[nedchu]

closes #595

Summary of changes

1. src/data_cell/compressed_graph_datacell.h Graph datacell with Elias-Fano encoder that can compress the adjacency list
2. src/data_cell/graph_storage_type.h Add GraphStorageTypes, can choose to use compressed graph, or sparse graph, or flat one

enum class GraphStorageTypes {
    GRAPH_STORAGE_TYPE_FLAT = 0,
    GRAPH_STORAGE_TYPE_COMPRESSED = 1
};

3. src/data_cell/graph_interface_test.h Sort neighbor sets in BasicTest if needed, elias-fano encoder will sort neighbor sets
4. src/impl/elias_fano_encoder.h: Update elias-fano encoder
   a. Data visibility change to public (to serialize CompressedGraphDatacell)
   b. Change DecompressAll interface (to fit CompressedGraphDatacell)

from
    Vector<InnerIdType>
    DecompressAll(Allocator* allocator) const;
to
    void
    DecompressAll(Vector<InnerIdType>& neighbors) const;

[codecov]

Codecov Report

Attention: Patch coverage is 94.61538% with 7 lines in your changes missing coverage. Please review.

@@            Coverage Diff             @@
##             main     #596      +/-   ##
==========================================
- Coverage   91.37%   91.36%   -0.02%     
==========================================
  Files         180      182       +2     
  Lines       10761    10837      +76     
==========================================
+ Hits         9833     9901      +68     
- Misses        928      936       +8     

Flag	Coverage Δ
cpp	91.36% <94.61%> (-0.02%)	⬇️

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Components	Coverage Δ
common	93.28% <ø> (-0.09%)	⬇️
datacell	92.03% <91.86%> (+0.04%)	⬆️
index	89.52% <ø> (-0.06%)	⬇️
simd	100.00% <ø> (ø)

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[wxyucs]

lgtm

[jiaweizone]

LGTM