Server reflection fails when using well-known types (Timestamp)

## Problem

Server reflection fails when using `google.protobuf.*` well-known types such as `Timestamp` or `Duration`, requiring them to be registered by the server as well for `grpcurl` to work properly.

## Setup

I am using `grpc-js` with NestJS integration along with `@grpc/reflection` to register all my `.proto` files on startup. It works exactly like [their example](https://github.com/nestjs/nest/blob/master/sample/04-grpc/src/grpc-client.options.ts). I also use [ts-proto](https://github.com/nestjs/nest/blob/master/sample/04-grpc/src/grpc-client.options.ts) for generating the TypeScript interfaces from my `.proto` files.

I can `grpcurl localhost:5051 list` to see my services as expect:

```
$ grpcurl -plaintext localhost:5051 list
core.Organizations
core.Users
```

However, once I try to list one that uses a `Timestamp` message I get the following error:

```
$ grpcurl -plaintext localhost:5051 list core.Organizations
Failed to list methods for service "core.Organizations": proto: message field "core.Organization.createdAt" cannot resolve type: "*.google.protobuf.Timestamp" not found
```

Interestingly, if I test it using the `-import-path` and `-proto` flags then it works fine!

```
$ grpcurl -plaintext -import-path ./proto -proto organizations.proto localhost:5051 describe core.Organizations
core.Organizations is a service:
service Organizations {
rpc GetOrganization ( .core.GetByIdRequest ) returns ( .core.Organization );
rpc GetOrganizationProfile ( .core.GetByIdRequest ) returns ( .core.OrganizationProfile );
}

$ grpcurl -plaintext -import-path ./proto -proto organizations.proto localhost:5051 describe core.Organization
core.Organization is a message:
message Organization {
string id = 1;
string displayName = 2;
optional string description = 3;
string type = 4;
string profileUsername = 5;
repeated .core.OrganizationProfileInfo profiles = 6;
.core.OrganizationContact contact = 7;
.core.OrganizationAddress address = 8;
optional string countryCode = 9;
optional string phoneNumber = 10;
optional string emailAddress = 11;
.google.protobuf.Timestamp createdAt = 12;
.google.protobuf.Timestamp updatedAt = 13;
}
```

I do not have any local copies of the Google well-known type `.protos` and my import looks like this in `organizations.proto`:

```
syntax = "proto3";

import "google/protobuf/timestamp.proto";
import "common.proto";

package core;
```

## Expectation

That `grpcurl` would have the Google well-known types pre-registered so that server reflection does not need to register them, which seems a bit redundant.