Replace proof_of_sql_parser::intermediate_ast::Literal and proof_of_sql_parser::intermediate_ast::Expression with sqlparser::ast::Expr in the proof-of-sql crate

[iajoiner]

Background and Motivation

This issue is a subtask in #235. In short since we plan to add more SQL features we plan to switch to the sqlparser crate which is a feature-rich, no_std-compatible parser used by DataFusion, which is part of the Arrow ecosystem.

Right now we already have some code that can convert intermediate AST from proof-of-sql-parser we use to sqlparser AST. Now we need to systematically replace instances of proof-of-sql-parser constructs with their corresponding sqlparser ones.

Changes Required

• Replace proof_of_sql_parser::intermediate_ast::Literal with sqlparser::ast::Expr in the proof-of-sql crate.
• Replace proof_of_sql_parser::intermediate_ast::Expression with sqlparser::ast::Expr in the proof-of-sql crate.

Notes:

• This issue is blocked until the following issues are complete:
  • Replace proof_of_sql_parser::intermediate_ast::UnaryOp with sqlparser::ast::UnaryOp in the proof-of-sql crate #348
  • Replace proof_of_sql_parser::intermediate_ast::BinaryOp with sqlparser::ast::BinaryOp in the proof-of-sql crate #349
  • Replace proof_of_sql_parser::Identifier with sqlparser::ast::Ident in the proof-of-sql crate #350
  • Adapt proof_of_sql_parser::posql_time to sqlparser #351
  • Replace proof_of_sql_parser::intermediate_ast::ResourceId with Vec<sqlparser::ast::Ident> or sqlparser::ast::ObjectName in the proof-of-sql crate #352
• The reason why we want to cast Literal to Expr as opposed to Value is that Value doesn't handle timestamp type. If you have a clever solution that can use Value instead of Literal it is even better but using Expr is what we currently expect.