Add support for plugins to specify binary request paths (#23729)

* wip

* more pruning

* Integrate OCSP into binary paths PoC

 - Simplify some of the changes to the router
 - Remove the binary test PKI endpoint
 - Switch OCSP to use the new binary paths backend variable

* Fix proto generation and test compilation

* Add unit test for binary request handling

---------

Co-authored-by: Scott G. Miller <smiller@hashicorp.com>

sdk/plugin/grpc_backend_server.go

@@ -9,8 +9,9 @@ import (
 	"fmt"
 	"sync"
 
-	log "github.com/hashicorp/go-hclog"
 	"github.com/hashicorp/go-plugin"
+
+	log "github.com/hashicorp/go-hclog"
 	"github.com/hashicorp/vault/sdk/helper/pluginutil"
 	"github.com/hashicorp/vault/sdk/logical"
 	"github.com/hashicorp/vault/sdk/plugin/pb"
@@ -196,6 +197,7 @@ func (b *backendGRPCPluginServer) SpecialPaths(ctx context.Context, args *pb.Emp
 			LocalStorage:          paths.LocalStorage,
 			SealWrapStorage:       paths.SealWrapStorage,
 			WriteForwardedStorage: paths.WriteForwardedStorage,
+			Binary:                paths.Binary,
 		},
 	}, nil
 }