Properly handle backslash escapes in patterns

When including Regex escapes in grok pattern definitions (and elsewhere), the `inspect` call on arrays (and by extension on arrays) renders the backslash as a double backslash, invalidating the pattern.

As a workaround, I now recurse into the array and create the string on my own instead of relying on inspect. Given the limited amount of data structures, it should be fine as well.