Refactor series implementation into its own module

This commit reorganizes the series-related code by moving the
`RingBuffer`, `ScalarSeries`, `ValueSeries`, `RecordSeries`,
`SeriesView`, and `SharedSeries` structs into a new
`src/ast/rtl/series/data.rs` file.

The `src/ast/rtl/series/mod.rs` file now contains the module
declaration, re-exports, and the `register` function for registering
series-related native functions with the environment. This improves code
organization and maintainability.

src/ast/environment.rs

@@ -19,7 +19,7 @@ use crate::ast::compiler::lambda_collector::LambdaCollector;
 use crate::ast::compiler::lowering::Lowering;
 use crate::ast::compiler::macros::{MacroEvaluator, MacroExpander, MacroRegistry};
 use crate::ast::compiler::optimizer::Optimizer;
-use crate::ast::compiler::specializer::{FunctionRegistry, MonoCache, Specializer};
+use crate::ast::compiler::specializer::{FunctionRegistry, MonoCache, RtlLookupFunc, Specializer};
 use crate::ast::rtl::{self, intrinsics};
 use crate::ast::types::{
     NativeFunction, NodeIdentity, Purity, SourceLocation, StaticType, Value,
@@ -28,8 +28,12 @@ use crate::ast::types::{
 use crate::ast::diagnostics::{DiagnosticLevel, Diagnostics};
 pub type PipelineGenerator = Box<dyn FnMut() -> bool>;
 
-const SYSTEM_LIB_SOURCE: &str = include_str!("system.myc");
-const SYSTEM_LIB_PATH: &str = "<embedded>/system.myc";
+const SYSTEM_LIB_SOURCE: &str = include_str!("rtl/prelude.myc");
+const SYSTEM_LIB_PATH: &str = "<embedded>/prelude.myc";
+
+fn make_rtl_lookup() -> RtlLookupFunc {
+    Rc::new(|name: &str, args: &[StaticType]| intrinsics::lookup(name, args))
+}
 
 pub struct CompilationResult {
     pub ast: Option<TypedNode>,
@@ -707,7 +711,7 @@ impl Environment {
             analyzed_registry: self.typed_function_registry.clone(),
         });
 
-        let rtl_lookup = Rc::new(|name: &str, args: &[StaticType]| intrinsics::lookup(name, args));
+        let rtl_lookup = make_rtl_lookup();
         let typed_reg = self.typed_function_registry.clone();
         let mono_cache = self.monomorph_cache.clone();
         let root_values = self.root_values.clone();
@@ -755,8 +759,7 @@ impl Environment {
                 let sub_registry = Rc::new(EnvFunctionRegistry {
                     analyzed_registry: typed_reg.clone(),
                 });
-                let sub_rtl_lookup =
-                    Rc::new(|name: &str, args: &[StaticType]| intrinsics::lookup(name, args));
+                let sub_rtl_lookup = make_rtl_lookup();
 
                 let sub_specializer = Specializer::new(
                     Some(sub_registry),