Add CLI formatting to deno_runtime

[cd-work]

This takes the existing fmt_error module from cli and puts it as a public module into deno_runtime.

While the module isn't big, its functionality is certainly useful for any application interested in providing a pleasant error output in a CLI environment. Because of this, I think it makes sense to expose this for other consumers, so the intricate edgecases don't have to be reinvented every time.

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This PR is mostly a suggestion for something that I think would be useful. The best approach to be taken is up for discussion I think, but considering I've already copied deno's module to enhance errors in my own application, I think it would be nice to make this easier for others that come after me.