Automatically reduce 0 and empty multiassets

[nielstron]

I noticed that the new ledger rules now disallow empty dicts and 0 values in multiassets. It would be good to anyways prevent this by design - this also always makes transactions cheaper. Here is an implementation proposal. I also tried to verify the non-emptiness strictness with an integration test but it seems to fail. We may want to remove it.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.33%. Comparing base (7243cd9) to head (b6e6dea).
Report is 1 commits behind head on chang.

Additional details and impacted files

@@            Coverage Diff             @@
##            chang     #372      +/-   ##
==========================================
+ Coverage   85.23%   85.33%   +0.09%     
==========================================
  Files          32       32              
  Lines        4153     4194      +41     
  Branches     1040     1055      +15     
==========================================
+ Hits         3540     3579      +39     
- Misses        428      429       +1     
- Partials      185      186       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[nielstron]

This PR does also not yet cover the possibility of creating a 0 value by hand (i.e. accidentally by adding stuff together)

[nielstron]

@cffls Can you maybe help with that last bit?
I think the fee computation may be thrown off somewhere - are we computing the wrong number of tokens?

FAILED test/test_zero_empty_asset.py::TestZeroEmptyAsset::test_submit_zero_and_empty - ogmios.errors.ResponseError: Ogmios responded with error: {'jsonrpc': '2.0', 'method': 'submitTransaction', 'error': {'code': 3122, 'message': "Insufficient fee! The transaction doesn't not contain enough fee to cover the minimum required by the protocol. Note that fee depends on (a) a flat cost fixed by the protocol, (b) the size of the serialized transaction, (c) the budget allocated for Plutus script execution. The field 'data.minimumRequiredFee' indicates the minimum required fee whereas 'data.providedFee' refers to the fee currently supplied with the transaction.", 'data': {'minimumRequiredFee': {'ada': {'lovelace': 189261}}, 'providedFee': {'ada': {'lovelace': 184861}}}}, 'id': None}

[nielstron]

Great, thank you @cffls
Will merge this into chang then unless you have further comments

[cffls]

Looks good to me! Please feel free to merge.