Resolves from an in-memory map of name to contents.
For tests, for Livebook, and for any caller that has the bytes and requires the include graph assembled without filesystem access.
Tptp.Unit.from_string(source,
resolver: {Tptp.Resolver.Map, files: %{"a.ax" => "fof(a, axiom, p)."}}
)Names are matched exactly as written in the include directive, so a map keyed
"Axioms/a.ax" does not resolve include('a.ax'). Path equivalence is
Tptp.Resolver.Fs's concern; a test resolver inferring it would admit tests that
pass for the wrong reason.