feat: Complete target system with C# bindings and resource inference (#458)

* feat: Add Schema Registry and Validation Framework

This commit introduces a comprehensive schema registry and validation framework, providing schema-based validation of resources and policy effects.

- Thread-safe, in-memory registry for schema storage and management
- Global registry patterns for effects and resources
- Concurrent access with proper error handling
- Unicode schema names support

- JSON Schema-compliant validation for all primitive types
- Advanced constraint validation (patterns, ranges, length limits)
- Discriminated union support with anyOf schemas
- Detailed error reporting with nested validation paths
- Discriminated subobject validation for polymorphic schemas

- **Registry Tests**: All registry operations
- **Effect Tests**: Policy effect validation
- **Resource Tests**: Resource validation
- **Validation Tests**: Core validation engine
- Thread-safety, error handling, integration scenarios, edge cases

- **Dependencies**: dashmap, once_cell, regex
- **Thread Safety**: Minimal locking with Rc<Schema> sharing
- **Error Types**: TypeMismatch, OutOfRange, PatternMismatch, etc.

- Complete schema registry and validation subsystem
- Comprehensive test coverage
- Foundation for policy validation in Regorus

Benchmarks:

- Criterion benchmarks for basic types, effects and Azure resources
- Performance range: 3.22ns (string) to 34.74µs (Azure VM resource schema validation)
- String withs patterns validation: 30.2µs. Need to explore whether regex caching helps
  bring this down.
- Azure policy effects: 188ns-1.4µs

Signed-off-by: Anand Krishnamoorthi <anakrish@microsoft.com>

* feat: Complete target system with C# bindings and resource inference

- Add comprehensive target system with TargetRegistry and target-aware compilation
- Implement resource type inference from policy equality expressions
- Create modular C# bindings with separate wrapper classes for each concept
- Add thread-safe CompiledPolicy with reference counting for safe disposal
- Enhance FFI with detailed error propagation and target functionality
- Create TargetExampleApp demonstrating Azure Policy integration
- Add CI/CD pipeline testing for all C# applications
- Support target definitions with schema validation and resource selectors
- Implement PolicyModule struct and target-aware compilation methods
- Add comprehensive test coverage for target functionality

Signed-off-by: Anand Krishnamoorthi <anakrish@microsoft.com>

---------

Signed-off-by: Anand Krishnamoorthi <anakrish@microsoft.com>

src/lib.rs

@@ -21,31 +21,44 @@ extern crate std;
 
 mod ast;
 mod builtins;
+mod compile;
+mod compiled_policy;
 mod engine;
 mod indexchecker;
 mod interpreter;
 mod lexer;
 mod number;
 mod parser;
+mod policy_info;
 #[cfg(feature = "azure_policy")]
-mod registry;
+pub mod registry;
 mod scheduler;
 #[cfg(feature = "azure_policy")]
 mod schema;
+#[cfg(feature = "azure_policy")]
+pub mod target;
 mod utils;
 mod value;
 
+#[cfg(feature = "azure_policy")]
+pub use {
+    compile::compile_policy_for_target,
+    schema::{error::ValidationError, validate::SchemaValidator, Schema},
+    target::Target,
+};
+
+pub use compile::{compile_policy_with_entrypoint, PolicyModule};
+pub use compiled_policy::CompiledPolicy;
 pub use engine::Engine;
 pub use lexer::Source;
-#[cfg(feature = "azure_policy")]
-pub use schema::{error::ValidationError, validate::SchemaValidator, Schema};
+pub use policy_info::PolicyInfo;
 pub use value::Value;
 
 #[cfg(feature = "arc")]
-use alloc::sync::Arc as Rc;
+pub use alloc::sync::Arc as Rc;
 
 #[cfg(not(feature = "arc"))]
-use alloc::rc::Rc;
+pub use alloc::rc::Rc;
 
 #[cfg(feature = "std")]
 use std::collections::{hash_map::Entry as MapEntry, HashMap as Map, HashSet as Set};