Fix linting errors in a number of core and tool files (partial)

- As part of this work I also started building out errors.ts which will be a cumulation of error helpers to better handle the challenging `catch (error: unknown)` requirement.
- More changes are to come, this is truly a partial change in order to not disrupt as many people as possible.

Part of https://b.corp.google.com/issues/411384603

packages/cli/src/utils/errors.ts

@@ -0,0 +1,18 @@
+export function isNodeError(error: unknown): error is NodeJS.ErrnoException {
+    return error instanceof Error && 'code' in error;
+}
+
+export function getErrorMessage(error: unknown): string {
+    if (error instanceof Error) {
+        return error.message;
+      } else {
+        // Attempt to convert the non-Error value to a string for logging
+        try {
+           const errorMessage = String(error);
+           return errorMessage;
+        } catch {
+            // If String() itself fails (highly unlikely)
+            return 'Failed to get error details';
+        }
+      }
+}