refactor(flex): Refine the schema definition of rt_mutable_graph

[zhanglei1949]

What do these changes do?

• Adapt to a schema definition, change modern_graph.yaml, bulk_load.yaml.
• Introduce new test to verify graph loading.
• All csr related params are put in x_csr_params
• Our schema definition support each label of Vertex has at least one primary key. But current implementation doesn't support Primary keys(Maybe supported later).

Other repos reflected by this PR: gstest, flex_ldbc_snb

Related issue number

Fixes #3077

[codecov-commenter]

Codecov Report

Merging #3079 (45a4dd3) into main (055654c) will decrease coverage by 32.10%.
The diff coverage is 0.00%.

❗ Current head 45a4dd3 differs from pull request most recent head 673f2a2. Consider uploading reports for the commit 673f2a2 to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #3079       +/-   ##
===========================================
- Coverage   74.73%   42.63%   -32.10%     
===========================================
  Files         100      100               
  Lines       10828    10817       -11     
===========================================
- Hits         8092     4612     -3480     
- Misses       2736     6205     +3469     

Files Changed	Coverage Δ
python/graphscope/analytical/udf/compile.py	25.05% <0.00%> (-66.27%)	⬇️
python/graphscope/tests/unittest/test_udf_app.py	0.00% <0.00%> (-38.62%)	⬇️

... and 60 files with indirect coverage changes

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