fix: only retry 5xx Cloud SQL Admin API errors (#375)

This commit fixes the retry behavior of the two SQL Admin API calls.

Any response that results in a 50x error will now be retried up to
5 times with exponential backoff. Using gaxios default exponential backoff.

Previously the Node Connector was only retrying 3 times and for
all error codes.

Updating gaxios version to have newer params available.

src/sqladmin-fetcher.ts

@@ -51,12 +51,20 @@ const defaultGaxiosHttpMethodsToRetry = [
 function setupGaxiosConfig() {
   gaxios.defaults = {
     retryConfig: {
-      retry: 3,
+      retry: 5,
       // Make sure to add POST to the list of default methods to retry
       // since it's used in IAM generateAccessToken requests that needs retry
       httpMethodsToRetry: ['POST', ...defaultGaxiosHttpMethodsToRetry],
       // Should retry on non-http error codes such as ECONNRESET, ETIMEOUT, etc
       noResponseRetries: 3,
+      // Defaults to: [[100, 199], [408, 408], [429, 429], [500, 599]]
+      statusCodesToRetry: [[500, 599]],
+      // The amount of time to initially delay the retry, in ms. Defaults to 100ms.
+      retryDelay: 200,
+      // The multiplier by which to increase the delay time between the
+      // completion of failed requests, and the initiation of the subsequent
+      // retrying request. Defaults to 2.
+      retryDelayMultiplier: 1.618,
     },
   };
 }