In shared preset repositories, some users will use a mix of Inherit
Config and Repo Config options with the existing JSON Schema.
As part of Renovate 43, we're removing the ability for any global
options to be usable in Repo Config, which would also mean that it's now
either a case of "ignoring warnings in my editor" and "using Global
Config JSON Schema", which isn't a great option.
We can instead create a third JSON Schema, one which is focussed on
shared presets that can include Inherit Config options.
This makes it clear that the repo config's JSON Schema should not be
used for anything Inherit Config.
As noted in #38727, it would be convenient to distribute a separate JSON
Schema that is explicitly for "global" / "admin" / "self-hosted"
configuration, separate to the repository configuration in our current
`renovate-schema.json`.
This gets wired in as an additional JSON file, and will have a different
set of configuration options in the future, noted by the `isGlobal`.
Closes#38727.
Jamie Tanna