Improve prospectus slow page build/query times

As a developer, I would like Prospectus build times to be faster to improve development speed, and reduce the time needed to deploy changes to the website.

Background

Gatsby includes a benchmarks directory (https://github.com/gatsbyjs/gatsby/tree/master/benchmarks) in its project that allows you to get estimates for speeds of various use cases. When running these benchmarks for roughly the same number of pages we create on prospectus (~13324), we see that our page queries, and especially our page builds are much slower than the benchmarks.

Gatsby create pages benchmark run:

...
success run static queries - 0.002 s
success Building production JavaScript and CSS bundles - 2.790 s
success run page queries - 24.041 s — 13324/13324 555.49 queries/second
success Building static HTML for pages - 16.841 s — 13324/13324 800.89 pages/second
info Done building in 71.14 sec

Gatsby markdown benchmark run:

...⠀
success run static queries - 0.004 s
success Building production JavaScript and CSS bundles - 13.045 s
success Rewriting compilation hashes - 0.073 s
success run page queries - 202.963 s — 13324/13324 65.67 queries/second
success Building static HTML for pages - 59.094 s — 13324/13324 228.98 pages/second
info Done building in 315.724 sec

The relevant portions from a prospectus build:

success run page queries - 279.872 s — 13323/13323 47.61 queries/second
success Building static HTML for pages - 322.152 s — 13323/13323 42.77 pages/second

Our page query speed is closer to the markdown benchmark, so that one may not be able to improved a ton, but it certainly seems like we can greatly improve our page build speed.

success run page queries - 3733.381 s — 13329/13329 3.57 queries/second

Another run of our page queries is absurdly slow

Acceptance Criteria
The page build speed (and hopefully the page query speed too) is improved to a level deemed acceptable by the team, with data collected on performance before and after the change.

Other Notes
https://www.gatsbyjs.org/blog/2019-01-28-building-a-large-ecommerce-website-with-gatsby-at-daniel-wellington/ has some notes on improving gatsby build times, although we likely will not want to take all the same steps they took for improving build time.

https://github.com/gatsbyjs/gatsby/issues/15628 Gatsby issue on this