populate: fail on inputs drawn that the flake doesn't have

Nix ignores an input that --override-input names but the flake doesn't
have, with a warning, so a misspelt input name in inputs draws nothing,
and the source keeps using its own input.

Before changing anything, populate locks the flake of each source that
draws inputs, with an empty flake in place of each input drawn, which
may be unreachable, and fails, naming the source and the input, unless
the flake has each input drawn.  Below an input drawn from a source, the
path continues in the flake of that source.

An edge case misspells an input of the source's flake, and one below an
input drawn from a source, both ways of drawing inputs.

0 files changed, 0 insertions, 0 deletions