Optimise mesh grid for VSI

[denproc]

Closes #335

Proposed Changes

• cache mesh grid to be used for Gabor filter generation and generation of coordinates

[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 #342 (894701a) into master (91a348e) will not change coverage. The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #342   +/-   ##
=======================================
  Coverage   92.01%   92.01%           
=======================================
  Files          34       34           
  Lines        2491     2491           
=======================================
  Hits         2292     2292           
  Misses        199      199           

Flag	Coverage Δ
unittests	92.01% <100.00%> (ø)

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Impacted Files	Coverage Δ
piq/vsi.py	100.00% <100.00%> (ø)