Symbolic key snapshotting in attest

[ssalbdivad]

The following should convert the symbolic key via the printable method:

const mySymbol = Symbol("mySymbol");

// current
attest({ [mySymbol]: 1 }).snap({});

// ideal
attest({ [mySymbol]: 1 }).snap({ "Symbol(mySymbol)": 1 });

We could have a config option for strict symbols to throw on symbolic snapshotting since it's technically not enforceable.