refactor: Improved target resolution

[frgfm]

This PR introduces the following modifications:

• improves the target resolution
• adds a unittest for mobilenet V3 large (which was failing before)

[codecov]

Codecov Report

Merging #174 (4a0f35f) into main (a5c6c51) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #174   +/-   ##
=======================================
  Coverage   96.64%   96.64%           
=======================================
  Files           7        7           
  Lines         387      387           
=======================================
  Hits          374      374           
  Misses         13       13           

Impacted Files	Coverage Δ
torchcam/methods/activation.py	97.56% <ø> (ø)
torchcam/methods/gradient.py	98.93% <ø> (ø)
torchcam/utils.py	84.61% <ø> (ø)
torchcam/methods/_utils.py	100.00% <100.00%> (ø)