Make Vpc's asynchronous, and remove all usages of deasync library.

[CyrusNajmabadi]

This should be reviewed with whitespace changes off.

Due the necessity to perform many async operations during creation, many parts of an
[awsx.ec2.Vpc] have become asynchronous. This is encoded using the normal Output<awsx.ec2.Vpc>
type. However, for convenience, many parts are also available as Promises, making it easy to use
from async code. Specifically:

1. awsx.ec2.Vpc.vpc has changed from an aws.ec2.Vpc to an Output<aws.ec2.Vpc>.
2. The properties and methods exposed off of awsx.ec2.Vpc (like publicSubnetIds) are now
   async (i.e. Promise<Output<string>[]>).

These changes should not impact most code. Code that creates and passes around a Vpc or accesses
properties off of the Vpc should continue to work. If there is code that needs to access the raw
values (for example, to iterate over the subnets of a Vpc) that can be written like so:

const vpc = new awsx.ec2.Vpc(...);
const ids = await vpc.publicSubnetIds;
for (const id of ids) {
    ...
}

[CyrusNajmabadi]

was helpful when tracking down some issues. i'd like to keep it.