Add RTL functions for arithmetic and comparisons

This commit introduces a new module `ast::rtl` to house the standard
runtime library functions for the language. It includes implementations
for arithmetic operators (+, -, *, /, //, %), logical operators (and,
or, xor, not), bitwise shifts (<<, >>), and comparison operators (=, <>,
<, >, <=, >=).

Additionally, a `date` function for parsing datetime strings has been
added. This enhances the language's capability to handle basic
mathematical and logical operations.
Add RTL functions for arithmetic and comparisons

This commit introduces the runtime library (RTL) functions for basic
arithmetic operations, logical/bitwise operations, and comparisons. It
also includes a `date` function for parsing datetime strings.
Integration tests have been updated to cover these new functionalities.

src/ast/rtl/mod.rs

@@ -0,0 +1,9 @@
+pub mod core;
+pub mod datetime;
+
+use crate::ast::environment::Environment;
+
+pub fn register(env: &Environment) {
+    core::register(env);
+    datetime::register(env);
+}