🚀 Feature Request [getBindingsProxy]: ensure that the getBindingsProxy utility has robust error handling

[dario-piotrowicz]

Describe the solution

The getBindingsProxy utility (introduced in #4523) should handle error scenarios gracefully.

When I've implemented it I wanted to get the basic functionality up and running and deal with the details incrementally.

One of such details is error handling, the utility should:

• error with a graceful/helpful error message if it can't find the toml file (or proceed without picking up bindings?)
• let the user know when they try to access external local Durable Objects and Services but those aren't found (similar to the next-dev service and do warnings)
• gracefully handle any other type of issue (like a wrong configuration)