fix(ext/node): gate constrained memory cgroup reads (#36218)
## Summary
- check `systemMemoryInfo` access before Linux and Android cgroup memory
reads
- preserve the permissionless `0` result on platforms where no cgroup
files are read
- cover denied system-memory access on Linux and Android
## Why
`process.constrainedMemory()` reads cgroup memory-limit files on Linux
and Android. Related memory APIs already route host memory reads through
the `systemMemoryInfo` access check, so this aligns the Node-compatible
path with that behavior.
## Tests
- `./tools/format.js --check`
- `cargo check -p deno_node`
- `cargo build --bin deno`
- `cargo test -p unit_node_tests --test unit_node -- process_test`
- rebuilt-runtime check on macOS with system access denied returns `0`
The Linux and Android denial branch is covered by platform CI.
