[Go] - Fix coverage to match "go test" (replaces sonar-go/issues/340)

SonarGo coverage and go test coverage show different results. We should match go test coverage to avoid confusion.

Let's take the following code as example:

// hello.go
package hello

import "rsc.io/quote"
import "fmt"

func Hello() string {

    fmt.Printf(
        "Hello")

    return quote.Hello()
}

func fn(myvar int) int {
    myvar =
        42
	
    return myvar
}

// hello_test.go
package hello

import "testing"

func TestHello(t *testing.T) {
    want := "Hello, world."
    if got := Hello(); got != want {
        t.Errorf("Hello() = %q, want %q", got, want)
    }
}

Let's first run go test

$ go test -coverprofile=coverage.out
HelloPASS
coverage: 50.0% of statements
ok  	example.com/hello	0.006s

If use gocov and gocov-xml to convert the output (gocov convert coverage.out | gocov-xml > coverage.xml) we see that it counts 4 lines to cover and 2 lines uncovered (50% coverage) It counts only one line for statements split on multiple lines.

SonarGo on the other hand will count 9 lines to cover and 4 lines uncovered (55.6% coverage):

• including empty lines in Hello and fn.
• counting multiple lines when a statement is split on multiple lines: fmt.Printf( \n "Hello") and myvar = \n 42

This ticket replaces https://github.com/SonarSource/sonar-go/issues/340 from the old sonar-go repository