x/evm/types: use ethtypes.Transaction.To for cheaper retrieval

[odeke-em]

Following suit with PR #828, this change cuts down the expenses
from using .To doubly; yet using the Go in-condition variable idiom.

Updates #826

[codecov]

Codecov Report

Merging #835 (d21c656) into main (a2f246c) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #835   +/-   ##
=======================================
  Coverage   57.31%   57.31%           
=======================================
  Files          72       72           
  Lines        5984     5984           
=======================================
  Hits         3430     3430           
  Misses       2357     2357           
  Partials      197      197           

Impacted Files	Coverage Δ
x/evm/types/access_list_tx.go	70.94% <100.00%> (ø)
x/evm/types/dynamic_fee_tx.go	78.61% <100.00%> (ø)
x/evm/types/legacy_tx.go	95.20% <100.00%> (ø)