…raph profiler

The flamegraph profiler now collects thread state information (GIL held,
GIL released, waiting for GIL, and garbage collection activity) during
sampling and displays it in an interactive statistics bar. This helps users
identify GIL contention and understand thread behavior patterns.

Statistics are calculated both in aggregate and per-thread. When filtering
the flamegraph to a specific thread, the display updates to show that
thread's metrics. In GIL-only profiling mode, GIL-related statistics are
hidden since they aren't meaningful in that context.

The collection logic was refactored to process each sample in a single pass
rather than iterating through threads multiple times. GC frame detection now
uses a shared helper that consistently handles both tuple and object frame
formats.

Per-thread GC percentages now use total samples as the denominator instead
of per-thread sample counts. This makes them directly comparable with
aggregate statistics and easier to interpret when threads appear in different
numbers of samples.

The JavaScript includes null checks for DOM access and validates data
availability before rendering. Tests verify the JSON structure, percentage
calculations, and edge cases like zero samples, using only public APIs.

… flamegraph profiler

Co-authored-by: ivonastojanovic <80911834+ivonastojanovic@users.noreply.github.com>