x/bank/types: fix AddressFromBalancesStore address length overflow

[cuonglm]

Description

addrLen is encoded in a byte, so it's an uint8. The code in
AddressFromBalancesStore cast it to int for bound checking, but wrongly
use "addrLen+1", which can be overflow.

To fix this, just cast addrLen once and use it in all places.

Found by fuzzing added in #9060.

Fixes #9111

---

Before we can merge this PR, please make sure that all the following items have been
checked off. If any of the checklist items are not applicable, please leave them but
write a little note why.

• Targeted PR against correct branch (see CONTRIBUTING.md)
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Code follows the module structure standards.
• Wrote unit and integration tests
• Updated relevant documentation (docs/) or specification (x/<module>/spec/)
• Added relevant godoc comments.
• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• Re-reviewed Files changed in the Github PR explorer
• Review Codecov Report in the comment section below once CI passes

[odeke-em]

LGTM, thank you @cuonglm! Kindly cc-ing @alessio @marbar3778

[codecov]

Codecov Report

Merging #9112 (3d039e0) into master (a4a6e05) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #9112   +/-   ##
=======================================
  Coverage   58.79%   58.79%           
=======================================
  Files         583      583           
  Lines       32750    32750           
=======================================
  Hits        19255    19255           
  Misses      11218    11218           
  Partials     2277     2277           

Impacted Files	Coverage Δ
x/bank/types/key.go	80.00% <100.00%> (ø)

[tac0turtle]

utACk

[robert-zaremba]

thanks for the fix. left 2 suggestions.

[odeke-em]

Thank you for the reviews @marbar3778 and @robert-zaremba! Thank you for the catch and for the PR @cuonglm!