feat(template_lib): improve API for extracting data from NFTs

[mrnaveira]

Description

• Added new get_non_fungibles method to vaults and buckets in template_lib, that returns all the NonFungible objects contained within.
• Added new engine operations to support the new method in both vaults and buckets

Motivation and Context

We expect templates to often read NFT data from buckets or vaults. Currently the only way to do it is doing something like:

 let seller_badge_id = &seller_badge_bucket.get_non_fungible_ids()[0];
 let seller_badge = ResourceManager::get(self.seller_badge_resource).get_non_fungible(&seller_badge_id);
 let nft_metadata = seller_badge.get_data::<Metadata>();

This PR adds a new method get_non_fungibles to vaults and buckets to we can write the previous example as:

 let seller_badge = seller_badge_bucket.get_non_fungibles()[0];
 let nft_metadata = seller_badge.get_mutable_data::<Metadata>();

How Has This Been Tested?

New unit test in the engine crate for the new methods

What process can a PR reviewer use to test or verify this change?

Call the new methods inside a template

Breaking Changes

• None
• Requires data directory to be deleted
• Other - Please specify

[github-actions]

Test Results (CI)

195 tests  +1   195 ✅ +1   1h 25m 9s ⏱️ - 17m 40s
 52 suites ±0     0 💤 ±0 
  2 files   ±0     0 ❌ ±0 

Results for commit 1c60c30. ± Comparison against base commit 63a1563.

♻️ This comment has been updated with latest results.

[sdbondi]

utACK