test: improve snapshots (#5521)

- before
  ```
  ${input}${"~".repeat(printWidth)}
  ${output}
  ```
- after
  ```
  ===options===
  ${options}
  ${" ".repeat(printWidth)}| printWidth
  ====input====
  ${input}
  ===output====
  ${output}
  =============
  ```

tests/flow/node_tests/basic_node_modules/__snapshots__/jsfmt.spec.js.snap

@@ -1,10 +1,17 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
-exports[`foo.js - flow-verify 1`] = `
+exports[`foo.js 1`] = `
+====================================options=====================================
+parsers: ["flow"]
+printWidth: 80
+                                                                                | printWidth
+=====================================input======================================
 var x = require('bar.js');
 console.log(x);
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+=====================================output=====================================
 var x = require("bar.js");
 console.log(x);
 
+================================================================================
 `;