Read sourcegraphAnonymousUid cookie value into HubSpot forms #2443

Created by: attfarhan

NOTE: moved over from https://github.com/sourcegraph/about/pull/2443 due to some oddity around the deploy preview on that PR. Approved by Felix and Aileen on that PR.

Closes https://github.com/sourcegraph/sourcegraph/issues/11658.

This PR populates the hidden anonymous user ID field in HubSpot forms with the cookie value in sourcegraphAnonymousUid.

For any HubSpot form created using our createHubSpotForm function, when the form loads, we will read the sourcegraphAnonymousUid cookie value and populate the anonymous_user_id field in the form with the value. One thing to note is that this PR also changes the polyfill we currently have for jQuery.

The polyfill is from this article, which outlines how to provide custom callbacks to embedded HubSpot forms without importing jQuery: https://www.unstack.com/blog/hubspot-on-form-submit-callbacks-without-jquery. The old polyfill was taken from https://community.hubspot.com/t5/APIs-Integrations/Form-callback-throws-unrelated-jquery-error/m-p/232127/highlight/true#M11023 AFAICT, and replacing it with the new code does not seem to have any side effects. This is generally frustrating as the HubSpot embedded forms have a hard dependency on jQuery, but this feels like a reasonable workaround.