[Proposal] Add option for all schema fields to be excluded from Inspect and JSON encoding

[Noah Betzen]

In order to help prevent excess logging of fields, it might be useful to allow either:

1. A application config setting for a repo to redact all fields by default. As an example:

```

config :friends, Friends.Repo,
  database: "friends",

  redact: :all

```

and/or

2. A schema attribute that does the same. As an example:

```

@redact :all
schema "users" do
  # ...
end

```

I assume the implementation would be somewhere in these files:

- https://github.com/elixir-ecto/ecto/blob/18288287f18ce205b03b3b3dc8cb80f0f1b06dbe/lib/ecto/schema.ex#L651

- https://github.com/elixir-ecto/ecto/blob/18288287f18ce205b03b3b3dc8cb80f0f1b06dbe/lib/ecto/changeset.ex#L4251

Relevant Bluesky thread: https://bsky.app/profile/nezteb.net/post/3lls67z2hmc2s