Limit sharp's concurrency (#53385)
Sharp by default spawns #cpu_cores threads to process images which could lead to large memory consumption. This PR caps the `concurrency` value especially on dev.
Locally I see a small memory improvement (10~20 MB) from this, but it will mostly affect long-running servers.
Related: https://github.com/lovell/sharp/issues/2607
Co-authored-by: Steven <229881+styfle@users.noreply.github.com>
