Refactor CIR regions to be in a separate array

Author: rtfeldman

src/cache.zig

@@ -284,10 +284,11 @@ test "NodeStore cache round-trip" {
         .data_1 = 42,
         .data_2 = 100,
         .data_3 = 200,
-        .region = .{ .start = .{ .offset = 0 }, .end = .{ .offset = 10 } },
         .tag = .expr_string,
     };
     const expr_idx = store.nodes.append(store.gpa, expr_node);
+    const region = base.Region{ .start = .{ .offset = 0 }, .end = .{ .offset = 10 } };
+    _ = store.regions.append(store.gpa, region);
 
     try store.extra_data.append(store.gpa, 1234);
     try store.extra_data.append(store.gpa, 5678);

src/check/canonicalize/CIR.zig

@@ -466,8 +466,8 @@ fn formatPatternIdxNode(gpa: std.mem.Allocator, pattern_idx: Pattern.Idx) SExpr
     return node;
 }
 
-test "Node is 24 bytes" {
-    try testing.expectEqual(24, @sizeOf(Node));
+test "Node is 16 bytes" {
+    try testing.expectEqual(16, @sizeOf(Node));
 }
 
 /// A working representation of a record field

src/check/canonicalize/Node.zig

@@ -12,7 +12,6 @@ const collections = @import("../../collections.zig");
 data_1: u32,
 data_2: u32,
 data_3: u32,
-region: base.Region,
 tag: Tag,
 
 /// A list of nodes.