Add configuring engine pool using ZOO_ENGINE_POOL environment variable (#7950)

* Add configuring engine pool using ZOO_POOL environment variable

* Rename to ZOO_ENGINE_POOL

Author: jtran

.env.development

@@ -14,3 +14,4 @@ RUST_BACKTRACE=1
 PYO3_PYTHON=/usr/local/bin/python3
 ZOO_HOST=https://api.$VITE_KITTYCAD_BASE_DOMAIN
 #KITTYCAD_API_TOKEN=$VITE_KITTYCAD_API_TOKEN
+#ZOO_ENGINE_POOL=pr-1234

rust/kcl-lib/src/execution/mod.rs

@@ -388,12 +388,13 @@ impl ExecutorContext {
     /// Create a new default executor context.
     #[cfg(not(target_arch = "wasm32"))]
     pub async fn new(client: &kittycad::Client, settings: ExecutorSettings) -> Result<Self> {
+        let pool = std::env::var("ZOO_ENGINE_POOL").ok();
         let (ws, _headers) = client
             .modeling()
             .commands_ws(
                 None,
                 None,
-                None,
+                pool,
                 if settings.enable_ssao {
                     Some(kittycad::types::PostEffectType::Ssao)
                 } else {