OPA conformance (#71)

- Remove unnecessary memory allocations
- Add --non-strict flag
- Ensure that only empty modules (ones without rules) are initialzed prior to evaluating rules.
- Record rule as entry for each of its prefixes.
  For example, for a rule a.b.c =... in package test, record it in
  rules["data.test.a"], rules["data.test.a.b"] and rules["data.test.a.b.c"]

  This allows evaluating the correct list of rules based on expessions
  a.b.c, a.b, a, data.test.a.b.c, data.test.a.b, data.test.a

Closes #69
Closes #70

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

examples/regorus.rs

@@ -10,10 +10,13 @@ fn rego_eval(
     input: Option<String>,
     query: String,
     enable_tracing: bool,
+    non_strict: bool,
 ) -> Result<()> {
     // Create engine.
     let mut engine = regorus::Engine::new();
 
+    engine.set_strict_builtin_errors(!non_strict);
+
     // Load files from given bundles.
     for dir in bundles.iter() {
         let entries =
@@ -130,6 +133,10 @@ enum RegorusCommand {
         /// Enable tracing.
         #[arg(long, short)]
         trace: bool,
+
+        // Non strict execution
+        #[arg(long, short)]
+        non_strict: bool,
     },
 
     /// Tokenize a Rego policy.
@@ -171,7 +178,8 @@ fn main() -> Result<()> {
             input,
             query,
             trace,
-        } => rego_eval(&bundles, &data, input, query, trace),
+            non_strict,
+        } => rego_eval(&bundles, &data, input, query, trace, non_strict),
         RegorusCommand::Lex { file, verbose } => rego_lex(file, verbose),
         RegorusCommand::Parse { file } => rego_parse(file),
     }