Use macro per-test-file

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

tests/cases/3-instructions@literals.snap

@@ -1,55 +0,0 @@
----
-source: tests/file_tests.rs
-expression: emit
-info:
-  input: "{{ if true }}\n    Hello World!\n{{ end }}"
-  context: {}
-input_file: tests/cases/literals.nomo
----
-VMInstructions {
-    labels: {
-        LabelSlot {
-            index: 0,
-        }: 7,
-        LabelSlot {
-            index: 2,
-        }: 7,
-    },
-    instructions: [
-        LoadLiteralToSlot {
-            source: [Literal(Bool(true))]"true" (6..10),
-            value: Bool {
-                value: true,
-            },
-            slot: VariableSlot {
-                index: 1,
-            },
-        },
-        JumpIfNotTrue {
-            emit_slot: VariableSlot {
-                index: 1,
-            },
-            jump: LabelSlot {
-                index: 2,
-            },
-        },
-        AppendContent {
-            content: "\n    " (13..18),
-        },
-        AppendContent {
-            content: "Hello World!" (18..30),
-        },
-        AppendContent {
-            content: "\n" (30..31),
-        },
-        Jump {
-            jump: LabelSlot {
-                index: 0,
-            },
-        },
-        AppendContent {
-            content: "\n    " (13..18),
-        },
-        NoOp,
-    ],
-}