ast.CommentGroup.Text() shouldn't be used to read expected test's outputs

[tbruyelle]

Description

filetest can provide the expected output by using a comment prefixed with // Output:. It's useful to assert for instance Render functions :

package main

import (
	"gno.land/r/gnoland/faucet"
)

func main() {
	println(faucet.Render(""))
}

// Output:
// # Community Faucet.
//
// Status: active.
// Balance: 200000000ugnot.
// Total transfers:  (in 0 times).
//
// Package address: g17rgsdnfxzza0sdfsdma37sdwxagsz378833ca4
//
// Admin: g1jg8mtutu9khhfwc4nxmuhcpftf0pajdhfvsqf5
//
//  Controllers:
//
//
//
// Per request limit: 350000000ugnot

When gnodev test executes this kind of test, it reads this comment and compare it with the test outputs. If it doesn't match, the test fails. The problem comes from how those comments are read, because it currently uses ast.CommentGroup.Text() method, which reduces multiple lines into one (see method comment).

So typically for the example above, it's not possible to

• run gnodev test -update-golden-tests
• run gnodev test
  without having a failure at the second run, because the 3 empty lines between Controllers and Per request limit are reduced to one before comparison.

Steps to reproduce

The example above doesn't exist yet in the codebase, it's part of a fix I wanted to provide for #621. Anyway it should be easy to reproduce by testing a Render that returns multiple empty lines.