feat: DSL operator codegen

[AlSchlo]

Problem

The query optimizer needs to generate type-safe Rust code for various logical and scalar operators. Manually writing these operators is error-prone and makes it difficult to maintain consistency across the codebase.

Summary of changes

Added code generation support for logical and scalar operators:

1. Core Code Generation

   • Implemented type-safe operator generation for both logical and scalar operators
   • Automatically generates enums, structs, and helper functions
   • Handles type parameters appropriately (Value, Relation, Scalar)

2. Generated Components (among others)

   // Generates enum definitions
   pub enum LogicalOperator<Value, Relation, Scalar> {
       Filter(Filter<Value, Relation, Scalar>),
       Join(Join<Value, Relation, Scalar>),
       // ...
   }
   
   // Generates operator structs
   pub struct Filter<Value, Relation, Scalar> {
       pub child: Relation,
       pub predicate: Scalar,
   }
   
   // Generates constructor functions
   pub fn filter<Relation, Scalar>(
       child: Relation,
       predicate: Scalar,
   ) -> LogicalOperator<OptdValue, Relation, Scalar> {
       LogicalOperator::Filter(Filter::new(child, predicate))
   }

3. Example Usage
   Input DSL:

   Logical Filter(child: Logical, predicate: Scalar)  derive { // stuff }

   Generated code (among others):

   pub struct Filter<Value, Relation, Scalar> {
       pub child: Relation,
       pub predicate: Scalar,
   }
   
   impl<Relation, Scalar> Filter<OptdValue, Relation, Scalar> {
       pub fn new(child: Relation, predicate: Scalar) -> Self {
           Self { child, predicate }
       }
   }

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.0%. Comparing base (44d26e2) to head (11bd4b9).

Additional details and impacted files

Files with missing lines	Coverage Δ
optd-dsl/src/analyzer/semantic.rs	94.7% <100.0%> (ø)
optd-dsl/src/gen/operator.rs	98.7% <100.0%> (ø)
optd-dsl/src/parser/expr.rs	86.3% <ø> (ø)
optd-dsl/src/parser/functions.rs	90.3% <ø> (ø)
optd-dsl/src/parser/mod.rs	96.9% <ø> (ø)
optd-dsl/src/parser/operators.rs	90.4% <ø> (ø)
optd-dsl/src/parser/patterns.rs	83.0% <ø> (ø)
optd-dsl/src/parser/types.rs	89.3% <ø> (ø)

[skyzh]

looks like this would conflict with #26 and need to decide who merges first

[skyzh]

consider support block comments in the language?