feat(core): read what the default build has from the schema

[KrimsN]

dnspatch#90 adds the full build tag and a lighter default build. This makes the builder read what a release has from its schema, instead of assuming it.

• schema.json of a release since then says in_default_build for every plugin. A plugin outside it (a notifier, rfc2136, yandexcloud, namecheap) points to the -full image; the config constructor says so under the provider cards.
• ping_url is in every build of those releases, so it no longer points to -full and no longer adds a ping tag.
• Schemas of older releases have no such field and are read as before: every retriever and provider in the ready-made image, ping_url and the notifiers only in -full. The bundled v0.4.4-rc.1 schema behaves exactly as it did.
• Tests for both readings; the golden check passes against a binary built from dnspatch#90 with -tags full and the schema it generates.

Safe to merge before the dnspatch release: nothing changes until a release with the new schema is fetched (npm run schemas).

Linear: DNS-79
Part of DNS-79