Send protocol fees from pool manager via FillRewards rather than BankMsg

[kaimen-sano]

Description and Motivation

We currently use BankMsg::Send when a swap has occurred to send the protocol fees to the whale-lair. This is not desired, as it does not allow the whale-lair contract to hook into receiving the assets.

Related Issues

Closes #312.

Adding a integration test for this behaviour this is hard due to CosmWasm/cw-plus#763. Unfortunately the cosmwasm team is not interested in addressing this issue.

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Checklist:

• I have read Migaloo's contribution guidelines.
• My pull request has a sound title and description (not something vague like Update index.md)
• All existing and new tests are passing.
• I updated/added relevant documentation.
• The code is formatted properly cargo fmt --all --.
• Clippy doesn't report any issues cargo clippy -- -D warnings.
• I have regenerated the schemas if needed cargo schema.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.50%. Comparing base (a8ebb95) to head (e180cc6).
Report is 1 commits behind head on release/v2_contracts.

Additional details and impacted files

@@                  Coverage Diff                  @@
##           release/v2_contracts     #334   +/-   ##
=====================================================
  Coverage                 89.49%   89.50%           
=====================================================
  Files                       261      261           
  Lines                     26646    26650    +4     
=====================================================
+ Hits                      23848    23852    +4     
  Misses                     2798     2798           

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[kerber0x]

There's a function in the ww-std package (whale_lair.rs) that contains a function that builds this message for you. We can refactor this in the future.

[kerber0x]

well done!