toml: support complex array-tables-array constructs (#12438)

vlib/toml/tests/array_of_tables_array_test.v

@@ -0,0 +1,24 @@
+import os
+import toml
+
+const (
+	toml_text = '[[a]]
+    [[a.b]]
+        [a.b.c]
+            d = "val0"
+    [[a.b]]
+        [a.b.c]
+            d = "val1"
+'
+)
+
+fn test_nested_array_of_tables() {
+	mut toml_doc := toml.parse(toml_text) or { panic(err) }
+
+	toml_json := toml_doc.to_json()
+
+	eprintln(toml_json)
+	assert toml_json == os.read_file(
+		os.real_path(os.join_path(os.dir(@FILE), 'testdata', os.file_name(@FILE).all_before_last('.'))) +
+		'.out') or { panic(err) }
+}