Slash amounts support

[maurolacy]

Related to https://github.com/osmosis-labs/mesh-security-sdk/pull/125.

Adds support for slashing based on historical evidence (double signing slashing), through slashing amounts instead of slash ratios.

There are still some limitations and there's room for improvement in the contracts side impls. Will be documented in a number of follow-up issues.

TODO:

• [x] Fix / adapt / extend tests.
• [ ] Improve coverage / Add tests.

[maurolacy]

Needs test fixes but otherwise looks good. Sorry for the earlier approval. 😂

Welcome. Yes, I'll continue working on this asap.

[codecov-commenter]

Codecov Report

Attention: 98 lines in your changes are missing coverage. Please review.

Comparison is base (4402153) 86.71% compared to head (1080a83) 86.26%.

Files	Patch %	Lines
contracts/consumer/converter/src/contract.rs	1.26%	78 Missing :warning:
contracts/consumer/virtual-staking/src/contract.rs	90.65%	2 Missing and 8 partials :warning:
contracts/consumer/converter/src/ibc.rs	0.00%	3 Missing :warning:
...ontracts/provider/external-staking/src/contract.rs	97.70%	1 Missing and 2 partials :warning:
contracts/provider/external-staking/src/ibc.rs	0.00%	2 Missing :warning:
...ontracts/consumer/virtual-staking/src/multitest.rs	0.00%	1 Missing :warning:
packages/apis/src/converter_api.rs	0.00%	0 Missing and 1 partial :warning:

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #179 +/- ## ========================================== - Coverage 86.71% 86.26% -0.45% ========================================== Files 81 81 Lines 14035 14253 +218 Branches 14035 14253 +218 ========================================== + Hits 12170 12295 +125 - Misses 1288 1389 +101 + Partials 577 569 -8 ```

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