Improve output handling

[MartinKolarik]

Related to #55. We currently print the API response itself and some additional information. The extra information should always go to stderr. For example:

$ globalping http https://cdn.jsdelivr.net/npm --method GET
> NA, US, (FL), Tampa, ASN:29802, HIVELOCITY, Inc.
Invalid URL. The URL structure is /npm/package@version/file.js

The first line should go to stderr and the second to stdout. This makes it easier to programmatically process just one part of the output and matches how other CLIs work. If someone wants both parts, they can still merge it via 2>&1.

[jimaek]

The output itself doesn't change in this case right?

[MartinKolarik]

No, but running globalping http https://cdn.jsdelivr.net/npm --method GET > file means you only get the second line in the file and the first stays in the terminal.

[MartinKolarik]

Note that this makes processing the output easier for the most common --limit 1 scenario, but it's still tricky as soon as there are multiple responses. Some research would be useful to see how other tools handle this problem. Current ideas:

• allow the user to specify an output directory, then write each response to a separate file in the directory,
• print some kind of separator between the responses,
• do nothing and let users handle this case by using --json | jq ?

[didil]

I believe PR #58 fixes this as the results separator > NA, US ... now goes to stderr