feat: make policy length limits configurable per engine (#624)

- Add PolicyLengthConfig struct with max_col, max_file_bytes, and
  max_lines fields, replacing hardcoded constants in the lexer.
- Add Engine::set_policy_length_config and clear_policy_length_config
  to allow callers to override the default limits.
- Add Source::from_contents_with_limits and from_file_with_limits for
  direct Source construction with custom limits; existing from_contents
  and from_file signatures are preserved using defaults.
- Add tests for default rejection, custom limits, and engine plumbing.
- Add bindings for C, C++, Python, WASM/JS, Java, Ruby, C#, Go

bindings/csharp/TestApp/Program.cs

@@ -20,6 +20,8 @@ w.Restart();
 
 var engine = new Regorus.Engine();
 engine.SetRegoV0(true);
+// Raise the default col limit to 2000
+engine.SetPolicyLengthConfig(new Regorus.PolicyLengthConfig(maxCol: 2000, maxFileBytes: 1048576, maxLines: 20000));
 
 w.Stop();
 var newEngineTicks = w.ElapsedTicks;