Update proto file definition of Read/WriteStateBytes RPCs (#37529)

* Update Read/WriteStateBytes RPCs to match hashicorp/terraform-plugin-go#531

* Run `make protobuf`

* Run `make generate`

* Update use of `proto.ReadStateBytes_ResponseChunk` in tests

* Fix how diagnostics are handled alongside EOF error, update ReadStateBytes test

* More fixes - test setup was incorrect

I think? I assume that a response would be returned full of zero-values when EOF is encountered.

Author: SarahFrench

internal/providers/provider.go

@@ -903,34 +903,6 @@ type WriteStateBytesResponse struct {
 	Diagnostics tfdiags.Diagnostics
 }
 
-type ReadStateBytesRequest struct {
-	// TypeName is the name of the state store to read state from
-	TypeName string
-	// StateId is the ID of a state file to read
-	StateId string
-}
-
-type ReadStateBytesResponse struct {
-	// Bytes represents all received bytes of the given state file
-	Bytes []byte
-	// Diagnostics contains any warnings or errors from the method call.
-	Diagnostics tfdiags.Diagnostics
-}
-
-type WriteStateBytesRequest struct {
-	// TypeName is the name of the state store to write state to
-	TypeName string
-	// Bytes represents all bytes of the given state file to write
-	Bytes []byte
-	// StateId is the ID of a state file to write
-	StateId string
-}
-
-type WriteStateBytesResponse struct {
-	// Diagnostics contains any warnings or errors from the method call.
-	Diagnostics tfdiags.Diagnostics
-}
-
 type GetStatesRequest struct {
 	// TypeName is the name of the state store to request the list of states from
 	TypeName string