Allow using strings as json paths

[ayZagen]

Currently vrl functions accepts query paths defined in jq like statements. However using strings as json paths is the most common way to interact with jsons

By accepting strings we could write functions like this:

fields = [".source_type", ".kubernetes.pod_ip"]
for_each(fields) -> |_index, value| {
  del(value)
}

Strictly related to #25

[jszwedko]

Thanks for opening this new issue @ayZagen ! I think it is the same as #67 . Would you agree?

[ayZagen]

yes, thas the same issue. closing in favor of #67 😀