Use macro per-test-file

Signed-off-by: Marcel Müller <neikos@neikos.email>

tests/cases/trim_whitespace.1-parsed.snap

@@ -0,0 +1,38 @@
+---
+source: tests/file_tests.rs
+expression: parsed
+info:
+  input: "{{ if test -}}\n    Hello {{= stuff -}}\n{{- end }}"
+  context:
+    stuff: Hemera
+    test: true
+---
+ParsedTemplate {
+    tokens: [
+        [LeftDelim]"{{" (0..2),
+        [Whitespace]" " (2..3),
+        [ConditionalIf]"if" (3..5),
+        [Whitespace]" " (5..6),
+        [Ident]"test" (6..10),
+        [Whitespace]" " (10..11),
+        [TrimWhitespace]"-" (11..12),
+        [RightDelim]"}}" (12..14),
+        [Whitespace]"\n    " (14..19),
+        [Content]"Hello" (19..24),
+        [Whitespace]" " (24..25),
+        [LeftDelim]"{{" (25..27),
+        [WantsOutput]"=" (27..28),
+        [Whitespace]" " (28..29),
+        [Ident]"stuff" (29..34),
+        [Whitespace]" " (34..35),
+        [TrimWhitespace]"-" (35..36),
+        [RightDelim]"}}" (36..38),
+        [Whitespace]"\n" (38..39),
+        [LeftDelim]"{{" (39..41),
+        [TrimWhitespace]"-" (41..42),
+        [Whitespace]" " (42..43),
+        [End]"end" (43..46),
+        [Whitespace]" " (46..47),
+        [RightDelim]"}}" (47..49),
+    ],
+}