perf(x/auth): only check memo when memo is present

[technicallyty]

Description

• changes the ValidateMemoDecorator ante handler to only check the memo if one is included in the tx, which saves adtl' gas as reading params incurs a flat read gas cost.

Closes: n/a

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[julienrbrt]

@technicallyty can you update

cosmos-sdk/baseapp/block_gas_test.go

Line 169 in f3a558c

baseGas := uint64(52864) // baseGas is the gas consumed before tx msg

for fixing the tests?

[technicallyty]

does this change need a changelog entry? @alexanderbez @julienrbrt @tac0turtle

[julienrbrt]

does this change need a changelog entry? @alexanderbez @julienrbrt @tac0turtle

Sure, why not one under improvements.

[codecov]

Codecov Report

Merging #13528 (ac07a8b) into main (89c65f4) will not change coverage.
The diff coverage is 100.00%.

❗ Current head ac07a8b differs from pull request most recent head 04247f5. Consider uploading reports for the commit 04247f5 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #13528   +/-   ##
=======================================
  Coverage   53.92%   53.92%           
=======================================
  Files         643      643           
  Lines       55464    55464           
=======================================
  Hits        29909    29909           
  Misses      23153    23153           
  Partials     2402     2402           

Impacted Files	Coverage Δ
x/auth/ante/basic.go	79.27% <100.00%> (ø)