Display more informative error information in TimeoutError response body

[caesarsol]

- Summary

Closes #1459, problem described with detail in relative issue.
There are more elegant ways to solve this, but I would delay them to later times. This is kind of a quick but solid workaround.

I also removed the colored ◈ from the response body (ANSI chars), and changed the console log message to include the same exact failure message of the response: "Function invocation failed" (was slightly different, creating confusion).

- Test plan

Tested as described in #1459 with a TimeoutError, and by manually causing a new Error in the code.
Knowing what else can cause an error would help in triggering other possible error types.

- Description for the changelog

• Error 500 "Function invocation failed" message is more informative in both response body and console log (for example a TimeoutError)

- A picture of a cute animal (not mandatory but encouraged)

Thanks! ;)

[erezrokah]

Thank you for this @caesarsol, I believe you'll need to run npm run format to fix the linting errors on CI

[caesarsol]

Sorry about that! I'll do whenever I find the time.

[caesarsol]

Rewrote commit!

[caesarsol]

Solved conflict and linting problem

[erezrokah]

@caesarsol sorry for the late follow up on this.
I made some additional fixes:

1. When err is not a lambda error, it is a string, not an error instance - changed the code accordingly.
2. When the error comes from lambda it was already logged by winston so no need to console.log it again (it is logged as JSON as the moment but that's another issue).
3. Extracted the custom validation Netlify CLI does on lambda response to a separate function.

Please let me know what you think.