Feature/file storage: DiskInterface and Index

[tom6311tom6311]

Brief

• Rewrite Index build/load/save/insert/delete operations
• Build DiskInterface, which is the standard interface for accessing file and index

Features:

1. Functions for file-related index operations:
   • DiskInterface::build_index_from_table_bin
   • DiskInterface::load_index
   • DiskInterface::save_index
2. Functions for memory-related index operations:
   • Index::insert
   • Index::delete
3. Implement Index ordering by raw bytes of primary key, rather than attr value with data type
   • RowPair: { row: u32, key_value: Vec\<u8> }
4. Design test cases for the new functionalities
5. Merge TableMeta of Index and File into one at DiskInterface
6. Merge FileError and IndexError into DiskError
7. Extract storage info structs and hierarchy checking logics to DiskInterface

Known Issues

• Index only support single-attr primary key currently

[todo[bot]]

add table-level folders to storage hierarchy

https://github.com/tigercosmos/StellarSQL/blob/6e63d272a276fe6a7cfff64f35f22132c20cd063/src/storage/file.rs#L19-L24

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This comment was generated by todo based on a TODO comment in 6e63d272a276fe6a7cfff64f35f22132c20cd063 in #21. cc @tom6311tom6311.