fix #4872: run env: use run_command() for country detection

fix #4872: run env: use run_command() for country detection

This fixes a rather longstanding issue [0][1] with the country
detection, in that it might get completely stuck and thus hangs the
installation.

This is due how Perl, signals and line reading interacts.

A minimal reproducer, how the installer currently works, looks like
this:
```
    #!/usr/bin/env perl

    use strict;
    use warnings;

    open (my $fh, '-|', 'sleep', '1000') or die;

    my $prev = alarm(2);
    eval {
	local $SIG{ALRM} = sub { die "timed out!\n" };

	my $line;
	while (defined ($line = <$fh>)) {
	    print "line: $line";
	}
    };

    alarm($prev);
    close($fh);
```

One might expect that this times out after 2 seconds, as specified in
`alarm(2)`. The thruth is that `$line = <$fh>` apparently prevents the
signal to go through. This then causes the installer to hang there
indefinitely, if `traceroute` never progresses - which seems to happen
on lots of (weird) networks, as evidently can be seen in the forum [1].

Proxmox::Sys::Command::run_command() handles of these weird cases, takes
care of the nitty-gritty details and - most importantly - interacts
properly with SIGALRM, so just use that instead.

This _should_ really fix that issue, but reproducing it 1:1 as part of
the installation process is _very_ hard, basically pure luck. But
rewriting the reproducer using run_command (in the exact same way that
this patch rewrites detect_country_tracing_to()) fixes the issue there,
so it's the best we can probably do.

NB: This causes that the traceroute command is now printed to the log
(as run_command() logs that by default), which we could also hide e.g.
through another parameter if wanted.

[0] https://bugzilla.proxmox.com/show_bug.cgi?id=4872
[1] https://forum.proxmox.com/threads/proxmox-installation-trying-to-detect-country.134301/

Signed-off-by: Christoph Heiss <c.heiss@proxmox.com>