In a previous PR we added the `include_all_fields`
parameter to `DebugWithDb` to allow it to
not create spurious dependencies.
This PR takes a different approach: we simply
ignore the dependencies created during debug
operations. This is risky as it can create
incorrect dependencies, but it is way more
convenient and seems like what users probably
want.
It also means that `DebugWithDb` has a simpler
signature that matches the `Debug` trait again,
which seems good to me.
This adds initial support for on-demand inputs by allowing new inputs to
be created with only a shared reference to the database. This allows
creating new inputs during a revision and therefore from inside tracked
functions.
