[Stacks 2.1] Consider defaulting to versioned-smart-contracts after 2.1 hardfork

[zone117x]

Related to #1341

The above PR adds the capability to create and deserialize the new versioned-smart-contracts tx types, which is helpful for projects to upgrade to before the 2.1 fork so that codebases are prepared for the fork.

However, the builder functions default to creating a Stacks 2.0 regular smart-contract tx type so that codebases don't create a bad tx type that won't work before the 2.1 fork.

Once the 2.1 hardfork is live, this library should then publish a new version that defaults to versioned-smart-contracts in order to avoid a lot of developer confusion when Clarity2 features are used in the contract source code, but the tx fails when the explicit clarityVersion arg is not specified.

This would ensure the typical usage will just work before and after Stacks 2.1:

const transaction = await makeContractDeploy({
  contractName,
  codeBody,
  senderKey
});

Alternatively, makeContractDeploy(...) could detect if 2.1 is live and use that for the default, but this would require an additional network call. And AFAIK there's currently not a great way to detect if 2.1 is live. Right now, it would involve something like:

async function is21HardforkLive(): Promise<boolean> {
  const req = await fetch(`/v2/data_var/ST000000000000000000002AMW42H/pox-2/configured?proof=0`);
  const body = await req.text();
  if (req.ok) {
    // This might only return true after "period 2" (after PoX cycle N+1 after the Stacks 2.1 fork), see https://github.com/stacksgov/sips/blob/c0fb33e0fc2b62e8e6d4ed85fb4b4aa289bb6042/sips/sip-015/sip-015-network-upgrade.md#specification
    // Might be more accurate to instead just `return true` here, i.e. if status is 2xx then pox-2 contract has been deployed, which I think means Stacks 2.1 has activated.
    return JSON.parse(body)['data'] === '0x03'; // Clarity boolean-true
  } else if (req.status === 404 && body === 'Data var not found') {
    return false;
  } else {
    throw new Error(`Unexpected response: ${req.status} - ${body}`);
  }
}

The first approach makes more sense to me, but I'm open to either or other suggestions.