The call site for language functions doesn't currently have a way to
handle complex diagnostics, so rather than appear to support them in the
protocol we remove the concepts of diagnostics for now. We do however
retain the argument index fields, which we can wrap in a
function.ArgError and get a little more precise hcl diagnostic from
expression.
This change ensures that providers receive the source private state and can store potentially differing private state as part of a move, rather than always copying the source private state to the target. This functionality has not yet been released and therefore there are no compatibility concerns.
* Update proto schema and provider interfaces with support for moved across resource type RPCs
* address comments
* remove unused functions
* remove support for flatmap format
