Set vpcConnector back to default, (e.g. no VPC connector) based on a defineString env var.

### Related issues

### [REQUIRED] Version info

**node:**

16

**firebase-functions:**

4.3.1

**firebase-tools:**

11.24.0

**firebase-admin:**

11.3.0

### [REQUIRED] Test case

I want to deploy the same function to multiple GCP projects, some with a vpcConnector and some without. Those without, I've set an env variable to "default" and would like to use this in a comparator to set the connector back to default (e.g. no connector.)

### [REQUIRED] Steps to reproduce

Given `ResetValue` is "...Special configuration type to reset configuration to platform default." I'd assume I'd be able to do...

```
import { ResetValue } from 'firebase-functions/lib/common/options';
const region = defineString('REGION');
const vpcConnector = defineString('MY_VPC_VALUE');

const vpcConnectorConfig = vpcConnector
.equals('default')
.thenElse(ResetValue, vpcConnector);

const runtimeOpts: functions.RuntimeOptions = {
timeoutSeconds: 540,
memory: '8GB',
vpcConnector: vpcConnectorConfig,
vpcConnectorEgressSettings: 'ALL_TRAFFIC'
};

export const myHttpFunc = functions
.region(region)
.runWith(runtimeOpts)
.https.onCall(async (data, context) => {
```

but

1. TS error, "Argument of type 'typeof ResetValue' is not assignable to parameter of type 'string | number | boolean | string[] | Expression'"
2. on deployment, if I cast ResetValue to any to work around the TS error, I receive an error:

> Error: Failed to load function definition from source: Failed to generate manifest from function source: Error [ERR_PACKAGE_PATH_NOT_EXPORTED]: Package subpath './lib/common/options' is not defined by "exports" in .../node_modules/firebase-functions/package.json

### [REQUIRED] Expected behavior

Able to set VPC connector to default value based on setting of built-in comparators

### [REQUIRED] Actual behavior

Type not allow / function deploy failed.

### Were you able to successfully deploy your functions?

No