fix: client side errors from unexpected null/undefined values

[mixu3]

Overview

This PR contains possible fixes for two types of client side errors.

(1) We received type errors that could not be reproduced that look like this:
error: Cannot read properties of null (reading 'getCoordinateSystems') stackTrace: TypeError: Cannot read properties of null (reading 'getCoordinateSystems')

This means that the ExtensionAPI was null somewhere in the code. Adding these null checks (!api) are harmless and will hopefully prevent these errors from occurring again.

(2) We received another type error when trying to read $metadata:
error: Cannot read properties of undefined (reading 'httpStatusCode') stackTrace: TypeError: Cannot read properties of undefined (reading 'httpStatusCode')

Changes for this include explicitly typing errors as IoTSiteWiseServiceExceptions and setting the errorCode to the error name (it was never supposed to be the http status code in the first place)

Verifying Changes

• Nothing broke from manual testing in storybooks
• Can successfully add, copy, and delete trend cursors in charts
• npm run test in source-iotsitewise package was successful

Legal

This project is available under the Apache 2.0 License.