Breaking change: Cannot find module '@grpc/proto-loader' (@grpc/grpc-js@1.1.4)

### Problem description



`@grpc/grpc-js@1.1.4` crashes on import



```

internal/modules/cjs/loader.js:796

    throw err;

    ^



Error: Cannot find module '@grpc/proto-loader'

Require stack:

- /tmp/test-grpc/node_modules/@grpc/grpc-js/build/src/xds-client.js

- /tmp/test-grpc/node_modules/@grpc/grpc-js/build/src/load-balancer-eds.js

- /tmp/test-grpc/node_modules/@grpc/grpc-js/build/src/load-balancer.js

- /tmp/test-grpc/node_modules/@grpc/grpc-js/build/src/resolving-load-balancer.js

- /tmp/test-grpc/node_modules/@grpc/grpc-js/build/src/channel.js

- /tmp/test-grpc/node_modules/@grpc/grpc-js/build/src/index.js

- /tmp/test-grpc/index.js

    at Function.Module._resolveFilename (internal/modules/cjs/loader.js:793:17)

    at Function.Module._load (internal/modules/cjs/loader.js:686:27)

    at Module.require (internal/modules/cjs/loader.js:848:19)

    at require (internal/modules/cjs/helpers.js:74:18)

    at Object.<anonymous> (/tmp/test-grpc/node_modules/@grpc/grpc-js/build/src/xds-client.js:20:21)

    at Module._compile (internal/modules/cjs/loader.js:955:30)

    at Object.Module._extensions..js (internal/modules/cjs/loader.js:991:10)

    at Module.load (internal/modules/cjs/loader.js:811:32)

    at Function.Module._load (internal/modules/cjs/loader.js:723:14)

    at Module.require (internal/modules/cjs/loader.js:848:19) {

  code: 'MODULE_NOT_FOUND',

  requireStack: [

    '/tmp/test-grpc/node_modules/@grpc/grpc-js/build/src/xds-client.js',

    '/tmp/test-grpc/node_modules/@grpc/grpc-js/build/src/load-balancer-eds.js',

    '/tmp/test-grpc/node_modules/@grpc/grpc-js/build/src/load-balancer.js',

    '/tmp/test-grpc/node_modules/@grpc/grpc-js/build/src/resolving-load-balancer.js',

    '/tmp/test-grpc/node_modules/@grpc/grpc-js/build/src/channel.js',

    '/tmp/test-grpc/node_modules/@grpc/grpc-js/build/src/index.js',

    '/tmp/test-grpc/index.js'

  ]

}

```



### Reproduction steps



```

npm init

npm install @grpc/grpc-js@1.1.4 

echo "require('@grpc/grpc-js')" > index.js

node index.js

```



### Environment

```

npm -v

6.13.4

node -v

v12.14.1

```

 - OS name, version and architecture: `Linux 5.4.57-1-MANJARO #1 SMP PREEMPT Fri Aug 7 09:54:45 UTC 2020 x86_64 GNU/Linux`

 - Node version 12.4.1

 - Node installation method nvm

 - Package name and version @grpc/grpc-js@1.1.4



### Additional context



[Here](https://github.com/grpc/grpc-node/blob/master/packages/grpc-js/src/xds-client.ts#L18) in production code is import of a module that is only in dev dependencies, see stack trace.



Previous version `@grpc/grpc-js@1.1.3` is working correctly. This is a breaking change in semver's patch update.

[]