Fix cache nginx upload limit in the Tuist Helm chart

The Tuist Helm chart now lets you configure the upload size limit for the cache nginx sidecar via a new cache.nginx.clientMaxBodySize value (defaulting to 10m). It also disables request buffering on the cache upload proxy paths so module upload parts stream straight through to the cache application. Previously, the cache sidecar fell back to nginx’s default body limit, which could cause valid Xcode module uploads to be rejected with 413 Request Entity Too Large before reaching the cache service.