…Path on inputs

This way, flake frameworks have access to the flake location even when
an error causes `self` not to evaluate.

... and do not add `meta` to the lock when formal is present, like
we do for `self`.

These are relevant for determining compatibility properties of functions.
- Can I add an attribute? Is it open for extension?
- If I omit an attribute that I'd be expected to add, does that lead to a conflict?
  Such a conflict arises when the function is closed and also binds all attributes
  using `@` syntax.

It also answers a related question: is the function defined using the strict syntax?
This is useful for explaining the misconception that changing a plain lambda to a
strict lambda is a no-op refactor. The fact that it makes the function strict is
overlooked and the error message, infinite recursion sends users into panic mode.
With the new functionStrict primop we can write functions that catch the mistake
before we enter it, which could be very helpful.

Inputs is not quite an appropriate name because of `self` and `meta`,
which aren't inputs.

This doesn't suggest that two is the total count, and I think it's
a nice way to phrase it, because the functions are related.

... and fix an incorrect use of `grep -v`