fix(core): show variable name in curlies type error

[eliangcs]

We've seen many developers getting confused by the error message Cannot reliable interpolate objects or arrays into a string. It can be hard to figure out which trigger or action is having an issue without knowing the variable being resolved.

This PR changes the error message from:

Cannot reliable interpolate objects or arrays into a string. We received an Array:
"1,2,3"

to

Cannot reliable interpolate objects or arrays into a string. Variable `bundle.inputData.foo` is an Array:
"1,2,3"

[xavdid]

nice, this is a good little improvement.

I was trying to see if we could pass in the trigger key as well to really point them there, but without changing the method signature, I'm not sure we can. Probably not worth it this second.

[stevelikesmusic]

That is a better message @eliangcs 👏 Looks good.