fix: minor 5.2 message fixes

[toteki]

• MsgBeginUnbond max amount calculation (not currently affecting mainnet due to zero incentive unbonding period)
• MsgLeveragedLiquidate CLI was not accepting empty denoms

[codecov]

Codecov Report

Merging #2148 (0305763) into main (7f05ad4) will decrease coverage by 0.87%.
The diff coverage is 77.79%.

❗ Current head 0305763 differs from pull request most recent head b802609. Consider uploading reports for the commit b802609 to get more accurate results

@@            Coverage Diff             @@
##             main    #2148      +/-   ##
==========================================
- Coverage   75.38%   74.52%   -0.87%     
==========================================
  Files         100      127      +27     
  Lines        8025     9981    +1956     
==========================================
+ Hits         6050     7438    +1388     
- Misses       1589     2039     +450     
- Partials      386      504     +118     

Impacted Files	Coverage Δ
ante/spam_prevention.go	75.92% <ø> (ø)
x/incentive/codec.go	47.82% <ø> (+9.89%)	⬆️
x/incentive/keeper/invariants.go	0.00% <0.00%> (ø)
x/leverage/client/tests/suite.go	100.00% <ø> (ø)
x/leverage/client/tests/tests.go	100.00% <ø> (ø)
x/leverage/keeper/borrows.go	75.93% <ø> (-2.64%)	⬇️
x/leverage/keeper/collateral.go	72.72% <ø> (-0.16%)	⬇️
x/leverage/keeper/errors.go	100.00% <ø> (ø)
x/leverage/keeper/exchange_rate.go	72.72% <ø> (ø)
x/leverage/keeper/genesis.go	87.23% <ø> (ø)
... and 60 more

... and 29 files with indirect coverage changes