[Andrii Havryliuk (h1k3r)]

1. Why is this change necessary?

See shopware/shopware#12385

2. What does this change do, exactly?

Changes tracking of spans:

• replaces array<string, SpanInterface> with array<string, SpanInterface[]> for spans stack
• adds stack for scopes

3. Describe each step to reproduce the issue or behaviour.

1. Configure shopware installation with OpenTelemetry (use Tempo to store traces and Grafana to view them)
2. Add code that creates spans with conflicting names (easeast way - use code snippet bellow in some storefront controller)

    public function index(SalesChannelContext $context, Request $request): Response
    {
        $this->doSomething(9);
        return new Response('ok');
    }

    private function doSomething(int $n): void
    {
        if ($n < 1) {
            return;
        }
        Profiler::trace('doSomething', function () use ($n) {
            usleep(1000 * 100);
            $this->doSomething($n - 1);
        });
    }

3. Call the page and check traces, result should be similar to screenshots

Before fix:

After:

4. Please link to the relevant issues (if any).

• closes Multiple spans with the same name overwrite each other shopware#12385