tools: enable linting for v8_prof_processor.js

`lib/internal/v8_prof_processor.js` was being excluded from linting, but
the only lint issue it has is that it cannot run in strict mode. Disable
the `strict` rule with a comment and remove the file from
`.eslintignore`.

PR-URL: #6262
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Roman Klauke <romaaan.git@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

.eslintignore

@@ -1,5 +1,4 @@
 lib/internal/v8_prof_polyfill.js
-lib/internal/v8_prof_processor.js
 lib/punycode.js
 test/addons/??_*/
 test/fixtures

lib/internal/v8_prof_processor.js

@@ -1,3 +1,4 @@
+/* eslint-disable strict */
 const scriptFiles = [
   'internal/v8_prof_polyfill',
   'v8/tools/splaytree',