fix(@aws-amplify/datastore): nextjs/swc broken build workaround

[svidgen]

Description of changes

NextJS 13 enables SWC by default, which sometimes mangles the the build. This PR does two things:

1. Adds integ tests for sample apps that attempt to trigger bad nextjs builds
2. Adds a workaround for one known case, where SWC was over-aggressively dropping a variable declaration, resulting in an exception several lines later.

Note: Depends on https://github.com/aws-amplify/amplify-js-samples-staging/pull/494

Issue #, if available

#10732

Description of how you validated changes

Runtime failures were seen as in #10732 with NextJS@13 prod builds. The breakage was isolated by inserting dummy console logs with unique strings to help us determine where we were in the resulting minified build. By doing so, we could see that a variable declaration and later assignment were being eliminated entirely. Setting the var to a default value caused SWC to leave the declaration in and resolved runtime issues.

One of the newly added integ tests (the "basic" one) successfully triggers the error in CI on prod builds without the fix. The fix makes it pass in CI.

Checklist

• PR description included
• yarn test passes
• Tests are changed or added
• Relevant documentation is changed or added (and PR referenced)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[iartemiev]

LGTM 👍🏻