* Set `GEM_HOME` env var based on the Ruby version in `$PATH` (i.e.
`3.2.0` for the AL2 build image, `3.3.0` for the AL2023 build image)
* Copy previous `jekyll-v4` test fixture to `jekyll-v4-al2` (uses AL2
build image)
* Update `jekyll-v4` test fixture to use Jekyll 4.3.3 (required for Ruby
3.3.0), and remove `package.json` so that it uses AL2023 build image
* Copy previous `middleman-v4` test fixture to `middleman-v4-al2` (uses
AL2 build image)
* Removed `package.json` from `middleman-v4` fixture, so that it uses
AL2023 build image
* Forces the AL2 build container image for fixtures that depend on it,
via `engines.node` in package.json for most cases.
* The `testDeployment()` function was updated to send
`projectSettings.nodeVersion` in the POST body, to mimic the behavior in
CLI.
* For Go, Ruby, and Python tests, the `projectSettings.nodeVersion`
property is set "globally" in the Jest setup file, so that individual
fixtures didn't need to be adjusted.
