feat: support Diregapic long running operation

[summer-ji-eng]

Before the implementation, diregapic LRO return unary with compute.v1.Operation. It require manual code to poll the operation until it finish.

async function waitGlobalOperation(operation, project) {
  const globalClient = new compute.GlobalOperationsClient({fallback: 'rest'});
  for (;;) {
    const [getResp] = await globalClient.get({
      project,
      operation: operation.name,
    });
    if (getResp.status === 'DONE') {
      break;
    } else {
      await new Promise(resolve => setTimeout(resolve, 4000));
    }
  }
}

After, the sample code to call insert LRO method

const [operation] = await client.insert({
    project,
    firewallResource: resource,
  });
  const [response, metadata, third] = await operation.promise();
  console.log(response.status === 'DONE') --------> output: true;

It support Compute 4 operation polling service:
GlobalOperations
RegionOperations
ZonalOperations
GlobalOrganizationOperations

This version is not support dynamic diregapic lro, will modify with gapic-generator-typescript recognize diregapic LRO with annotation.

[alexander-fenster]

Leaving a comment to make sure this does not get checked in :)

[alexander-fenster]

This method should either be static or be defined outside of the class since it never accesses this.

[alexander-fenster]

I believe there is no cancellation for diregapic. Can we just throw?

if (this.diregapic) { 
  throw new Error("Cancellation is not supported for this method");
}

@vam-google what do you think?

[alexander-fenster]

Summoning @vam-google to check the logic of this method.

[alexander-fenster]

May I ask you to move this to a separate file? 1000+ lines is a lot :) This will also simplify all the test initialization code since you won't need to do if (diregapic) in it.

[alexander-fenster]

Thanks @summer-ji-eng, it looks great! Left some comments, mostly style+readability. I'll defer reviewing the DIREGAPIC-specific logic to @vam-google.