Speed up importing from local directory

[thekid]

This pull request greatly improves the import command's performance when importing journeys by reducing the number of API calls it makes:

• Before, one call to the Dialog API was made for each child. Children are now fetched along with the first API call.
• Google maps API lookups are only performed if the description file has changed.

Performance comparison

(For a run where nothing in the Album/oman-2024 directory has changes since the last import)

Before:

$ time xp import Albums/oman-2024/ $LOCAL
[+] [
  slug => "oman-2024"
  date => 2024-11-07 20:00:00+0100
  title => "Sultanat Oman"
# ...hundreds of lines of output
real    0m18.584s
user    0m0.015s
sys     0m0.030s

After:

$ time xp import Albums/oman-2024/ $LOCAL
[+] de.thekid.dialog.import.Journey<oman-2024>
 => Fetching entry oman-2024: ✓
 => Finished at Mon, 30 Dec 2024 14:38:07 +0000

real    0m0.649s
user    0m0.000s
sys     0m0.031s

Implementation status

• Journeys
• Contents
• Cover image

[thekid]

This used to include the following:

/** Executes a given external command and returns its exit code */
private function execute(string $command, array<string> $args, $redirect= null): void {
  $p= new Process($command, $args, null, null, [STDIN, $redirect ?? STDOUT, STDERR]);
  if (0 === ($r= $p->close())) return;

  throw new IllegalStateException($p->getCommandLine().' exited with exit code '.$r);
}

// FIXME: Uploading files that take longer than ~30 seconds is, for some reason,
// broken, and will result in a) the import tool crashing and b) the server ending
// up in an endless blocking loop. Use `curl` for videos instead.
if ('video' === $kind) {
  $this->execute('curl', [
    '-#',
    '-X', 'PUT',
    '-H', 'Authorization: '.$this->api->headers()['Authorization'],
    '-F', $kind.'=@'.strtr($target->getURI(), [DIRECTORY_SEPARATOR => '/']),
    $resource->uri(),
  ], ['null']);
} else {
  $transfer[$kind]= $target;
}

...which we might need to reinstate after integration-testing this PR.