fix: add AbortController polyfill for pre-warm lambda requests in onSuccess build step

[ericapisani]

Summary

In the initial release of #376 , the minimum version of node was increased to v14.17.0 because that was when the AbortController that's used in the pre-warm requests to the lambdas in the onSuccess was first included within the Node global object.

However, AbortController is controlled by a feature flag in v14, leading to errors of it not existing when building sites with the plugin.

Changes

• Add an AbortController polyfill to support Node v14.17+
• Remove references to globalThis - this was incorrectly added in the initial implementation
• Update imports from node:process to process. This was being raised as an error in Node v14

Test plan

Deploy previews aren't how one would reproduce the error. To reproduce (in local environment):

• Install Node v14.17.0
• Attempt to build the demo site with the GATSBY_EXCLUDE_DATASTORE_FROM_BUNDLE environment variable enabled

If one were to do this prior to these changes, you should see an error that looks like globalThis.AbortController is not a constructor.

After these changes, the site should correctly build and deploy

Relevant links (GitHub issues, Notion docs, etc.) or a picture of cute animal

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[ascorbic]

I haven't tested this locally, but it looks good to me

[sarahetter]

Tested locally and it works as described!

[ascorbic]