Support getting the current local and global vars in scope in a snapshot dump

Right now, if you suspend a Monty VM at a host call, you only get the ability to see that function call (and resume execution). You can't see information about the values of local and global vars for debugging.

It would be great to have a public method on SyncSnapshot called snapshot.inspect() (or similar) that gives you back all the local and global variables with data about where those vars are in the code monty is executing. Similar to what is exposed on Frame objects today, but for the vars themselves https://pydantic.dev/docs/monty/api/python/errors/#pydantic_monty.Frame

Related: https://github.com/pydantic/monty/issues/847 Also talked here about this: https://pydanticlogfire.slack.com/archives/C0AEZ9EQT0F/p1788983343955609