fix!: leverage.MaxBorrow return zero instead of failing when there is no more to borrow

[robert-zaremba]

Description

ref: #1690 (comment)

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[gsk967]

LGTM

[gsk967]

@robert-zaremba can you fix failing tests

[codecov-commenter]

Codecov Report

Merging #1694 (53a4387) into main (38c2d04) will decrease coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1694      +/-   ##
==========================================
- Coverage   57.55%   57.53%   -0.03%     
==========================================
  Files          75       75              
  Lines        7925     7928       +3     
==========================================
  Hits         4561     4561              
- Misses       3014     3016       +2     
- Partials      350      351       +1     

Impacted Files	Coverage Δ
x/leverage/keeper/limits.go	59.29% <ø> (-1.40%)	⬇️
x/leverage/keeper/keeper.go	69.27% <100.00%> (+0.16%)	⬆️
x/leverage/keeper/msg_server.go	79.06% <100.00%> (-0.52%)	⬇️

[toteki]

A couple bits of cleanup, but looks good overall

[adamewozniak]

imo we should probably not scope creep this into v4

[toteki]

Looks like we got everything - once that uToken check is hopefully added to queryMaxWithdraw, should be good to merge