Add Rust GBT config flag

backend/src/__tests__/config.test.ts

@@ -40,6 +40,7 @@ describe('Mempool Backend Config', () => {
         AUDIT: false,
         ADVANCED_GBT_AUDIT: false,
         ADVANCED_GBT_MEMPOOL: false,
+        RUST_GBT: false,
         CPFP_INDEXING: false,
         MAX_BLOCKS_BULK_QUERY: 0,
         DISK_CACHE_BLOCK_INTERVAL: 6,