FIX: time_interpolation

[kmuehlbauer]

• [x] Tests added
• [x] Changes are documented in history.md

As reported by @egouden in #114 there are issues with time interpolation in some corner cases. While adding a test for this I've found there are more things involved which need changing. This PR addresses (hopefully) all of this.

• only interpolate of NaT present
• handle NaT correctly (-9223372036854775808)
• handle a1gate properly (roll data to first measured ray)
• derive interpolation angles using diff
• handle wrap around angles for PPI
• fix spurious digits introduced by floating point interpolation

Supersedes #114

[codecov[bot]]

Codecov Report

Merging #117 (98dfdbf) into main (6fe2ea0) will increase coverage by 0.09%. The diff coverage is 89.09%.

@@            Coverage Diff             @@
##             main     #117      +/-   ##
==========================================
+ Coverage   88.08%   88.17%   +0.09%     
==========================================
  Files          19       19              
  Lines        3297     3333      +36     
==========================================
+ Hits         2904     2939      +35     
- Misses        393      394       +1     

Flag	Coverage Δ
unittests	88.17% <89.09%> (+0.09%)	:arrow_up:

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

Impacted Files	Coverage Δ
xradar/io/backends/cfradial1.py	86.39% <0.00%> (ø)
xradar/io/backends/furuno.py	91.41% <0.00%> (ø)
xradar/io/backends/iris.py	84.85% <0.00%> (ø)
xradar/io/backends/odim.py	84.98% <0.00%> (ø)
xradar/io/backends/rainbow.py	92.10% <66.66%> (-0.21%)	:arrow_down:
xradar/util.py	97.27% <97.77%> (+0.78%)	:arrow_up:
xradar/io/backends/gamic.py	86.16% <100.00%> (ø)
xradar/model.py	96.19% <100.00%> (+0.02%)	:arrow_up:

[kmuehlbauer]

OK, let's get this in then.