Improve error messaging for KV package

[asteurer]

I have a Spin app where I use a key-value store for something. I neglected to include a path to a key-value store in the spin.toml file, and I got an error when I tried opening the default store:

My code:

let store = openDefault();

The error:

Error while running request handler: cyclic object value
Stack:
  r/<@build/precompiled-source.js:58:1681
  s@build/precompiled-source.js:58:2089
  fetch@build/precompiled-source.js:58:1402
  async*@build/precompiled-source.js:9588:30

This error is not very helpful haha. I'm wondering what things could be done to improve the error message?

On a related note, maybe there are other things in the spin.toml that would throw errors if improperly configured. Might be worth making this part of a larger discussion.

[karthik2804]

This will be fixed once #379 merges and a release is made.

But good pointon errors for others things. I'll have to take a look.