[Client] Expose Blueprints v2 runner via a feature flag

[adamziel]

Motivation for the change, related issues

Exposes the Blueprints v2 data flows via a ?experimental-blueprints-v2-runner=yes query API arg. Blueprints v2 won't actually execute yet. This PR only allows triggering the boot flow. For a functional Blueprint v2 execution, we'll need a few more PRs.

Testing Instructions (or ideally a Blueprint)

Go to this URL and confirm you're getting an error "Invalid blueprint: must NOT have additional properties at ":

http://127.0.0.1:5400/website-server/?experimental-blueprints-v2-runner=yes&php=8.3#{%22version%22:2}