[OSS site] Update all instrumentation to use tessen

[LizBaker]

This ticket is blocked by https://github.com/newrelic/gatsby-theme-newrelic/issues/559

Acceptance Criteria:

note 1st, verify if the site has any browser agent page actions that were not covered by the theme changes

• [x] Bring in new version of the theme
• [x] Check all instances of the instrumentation prop and make sure it follows the correct tessen formatting (category is Title Case, event name is camelCase)
• [x] Check for any uses of the useInstrumentedHandler hook and make sure it’s formatted correctly for tessen
• [x] Check for any uses of the browser agent directly (window.newrelic.pageAction)
• [x] Update any documentation/wiki references to the browser events
• [x] Update any dashboards that may be using the old browser events (events should be listed in the wiki but may not be up to date. You can also run this query to get a list of currently firing browser actions ((some may be coming from theme components))

Here are some important dashboards to look out for:

• [DevEn] Open Source Website
  • Every one of these dashboards seems broken, we should fix those as part of this effort.

[rudouglas]

I'm seeing the following error in Gatsby build but it doesn't seem to affect the sending of Tessen events:

warn Error persisting state: ({ location, env }) => ({
              path: location.pathname,
              env: env === 'production' ? 'pro...<omitted>...}) could not be cloned.

Removing this also doesn't change anything, location and env attributes are added to the event anyway, so i'm wondering if we actually need this?