Process-wide default. The simple allocator is stateless (every allocate
mints an independent buffer; refresh/release/needsRefresh are no-ops),
so a single shared instance is safe and avoids minting one allocator per
buffer. Used whenever no custom allocator is injected.
Process-wide default. The simple allocator is stateless (every
allocatemints an independent buffer;refresh/release/needsRefreshare no-ops), so a single shared instance is safe and avoids minting one allocator per buffer. Used whenever no custom allocator is injected.