…24292)

## Issue

The `Allocations` CI job can fail on PRs with a 1-allocation `Sys allocs` difference that local `cargo allocs` cannot reproduce. #22621 fixed one instance of this in the transformer stage. #24112 and #24017 hit the same failure again in the minifier stage: `kitchen-sink.tsx` measures 2309 Sys allocs on macOS/arm64 but 2310 on Linux/x64, so whichever platform regenerates the snapshot last breaks CI for the other.

## Why

The tracker counts every call to the system allocator. That includes the chunks bump arenas request. Whether an arena needs one more chunk depends on the total number of bytes in the arena, and byte totals are not the same on every target. For example, hashbrown tables use 16-byte control groups on x86_64 but 8-byte groups on aarch64. When an arena's content size sits close to a chunk boundary, one target crosses it and the other does not.

In the observed failure, the minifier's mangler-phase semantic build creates a fresh `Scoping`. Its arena holds symbol names, resolved-reference vectors, and the per-scope `bindings` hash tables, which are slightly larger on x86_64. The traced Linux-only allocation happened under `Scoping::add_resolved_reference -> ArenaVec::push -> Arena::new_chunk`, when the push overflowed the current chunk and requested a new 720880-byte chunk. On aarch64 the same content fit in the existing chunk, so the count stayed one lower.

Every other allocation class in the measurement grows on element counts, which are identical across platforms. Logging every allocation size during the minifier stage on macOS/arm64, Linux/arm64, and Linux/x64 showed the three sequences match one-to-one except for arena chunk requests.

Any PR that shifts arena content near a chunk boundary can trip this again in any stage, so fixing one stage at a time does not close the class.

## Fix

Count chunk allocations in `oxc_allocator` under the tracker-only `track_allocations` feature, and subtract them from the reported Sys allocs in the tracker. The counter is global rather than per-arena because short-lived arenas (like the one backing `Scoping`) are created and dropped inside the measured operation.

Arena usage is still measured by the `Arena allocs` / `Arena reallocs` columns; only the platform-sensitive chunk-request count is excluded from `Sys allocs`.

Parser and transformer rows are unchanged (the main arena is pre-warmed, and #22621 already removed transformer scoping growth). Semantic, minifier, and formatter rows drop by their per-stage chunk counts.

## Validation

`cargo allocs` produces byte-identical snapshots on macOS/arm64, Linux/arm64 (Docker), and Linux/x64 (Docker), and is idempotent across reruns. `cargo test -p oxc_allocator` passes; clippy is clean with `track_allocations` both on and off, and the counter compiles out entirely without the feature.

AI usage: AI assistance was used to investigate, implement, and validate this change.