Fix Kotlin/Wasm bindgen runtime compilation on Kotlin 2.3.21

[IRus]

Problem

The Kotlin/Wasm 2 compilers × 2 EH encodings CI job fails when building the wasmWasi compatibility fixture pinned to Kotlin 2.3.21:

```
e: KwasmWasmGuestRuntime.kt:5:24 Unresolved reference 'ComponentModelInternalApi'
e: KwasmWasmGuestRuntime.kt:20:27 Unresolved reference 'componentModelRealloc'
e: KwasmWasmGuestRuntime.kt:21:27 Unresolved reference 'freeAllComponentModelReallocAllocatedMemory'

Task :bindgen-api:compileTestKotlinWasmWasi FAILED
```

Root cause

WasmGuestRuntimeRenderer emits a generated guest runtime that referenced kotlin.wasm.unsafe.componentModelRealloc, freeAllComponentModelReallocAllocatedMemory, and the ComponentModelInternalApi opt-in. These symbols only exist in Kotlin 2.4.0+, so the compatibility gate — which deliberately builds the fixture on the previous stable compiler (2.3.21) — could not compile it.

Fix

Replace the Component Model realloc allocator with an equivalent bump allocator built on withScopedMemoryAllocator (present in both 2.4.0 and 2.3.21). The guest allocator now tracks live regions in a map and replays the live prefix before each new allocation so returned pointers stay disjoint from regions the host still owns. The free path drops the freeAllComponentModelReallocAllocatedMemory reset.

Adds a regression assertion that the rendered runtime uses withScopedMemoryAllocator and no longer references componentModelRealloc.

Verification

• ✅ scripts/verify-kotlin-wasm-compiler-compatibility.sh — BUILD SUCCESSFUL on both rows: Verified Kotlin/Wasm compiler rows: 2.4.0, 2.3.21
• ✅ :bindgen-ksp:test (incl. BindingSourceRendererTest) — green

Note

This addresses only the compiler-compatibility failure. A separate, independent CI failure (Unknown host target: linux aarch64 on the Linux arm64 tests matrix entry) will be handled in a follow-up PR — Konan does not support linux aarch64 as a host, so that matrix entry needs restructuring regardless of this fix.