Configurable HTTP timeouts and connection limit for downloads

The CLI’s HTTP timeouts and per-host connection limit are now configurable via environment variables, letting self-hosted operators and anyone on a constrained network tune for slower paths. New variables: TUIST_HTTP_TIMEOUT_INTERVAL_FOR_RESOURCE (default 90), TUIST_HTTP_TIMEOUT_INTERVAL_FOR_REQUEST (default 120), and TUIST_HTTP_MAXIMUM_CONNECTIONS_PER_HOST (default 20). Raising the resource timeout lets a slow-but-recoverable download finish as a cache hit instead of falling back to a build-from-source.