Batch-wise computation of features for feature-based metrics

[snk4tr]

Closes #214

Proposed Changes

• Batch-wise computation of features for feature-based metrics
• Invoke CUDA empty cache to de-allocate GPU memory after features computation
• Add some files to .gitignore

[sonarcloud[bot]]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication

[sonarcloud[bot]]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication

[codecov[bot]]

Codecov Report

Merging #325 (64daca1) into master (27db4f3) will increase coverage by 0.45%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #325      +/-   ##
==========================================
+ Coverage   91.50%   91.96%   +0.45%     
==========================================
  Files          34       34              
  Lines        2485     2490       +5     
==========================================
+ Hits         2274     2290      +16     
+ Misses        211      200      -11     

Flag	Coverage Δ
unittests	91.96% <100.00%> (+0.45%)	:arrow_up:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
piq/base.py	90.32% <100.00%> (+1.86%)	:arrow_up:
piq/iw_ssim.py	100.00% <0.00%> (+0.50%)	:arrow_up:
piq/vsi.py	100.00% <0.00%> (+2.02%)	:arrow_up:
piq/fsim.py	100.00% <0.00%> (+2.89%)	:arrow_up:
piq/srsim.py	99.00% <0.00%> (+3.96%)	:arrow_up: