FEAT: Implement IntervalSub for pandas backend

[toryhaavik]

closes #1490

[codecov]

Codecov Report

Merging #1951 into master will decrease coverage by 1.75%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1951      +/-   ##
==========================================
- Coverage   87.68%   85.93%   -1.76%     
==========================================
  Files          93       93              
  Lines       16971    16971              
  Branches     2145     2145              
==========================================
- Hits        14881    14584     -297     
- Misses       1681     1972     +291     
- Partials      409      415       +6

Impacted Files	Coverage Δ
ibis/pandas/execution/temporal.py	86.04% <ø> (+0.77%)	⬆️
ibis/bigquery/client.py	41.1% <0%> (-53.39%)	⬇️
ibis/bigquery/compiler.py	59.92% <0%> (-37.5%)	⬇️
ibis/bigquery/udf/api.py	80.48% <0%> (-14.64%)	⬇️
ibis/impala/compiler.py	91.23% <0%> (-5.2%)	⬇️
ibis/pandas/dispatch.py	95.45% <0%> (-4.55%)	⬇️
ibis/pandas/client.py	85.54% <0%> (-3.47%)	⬇️
ibis/bigquery/api.py	63.33% <0%> (-3.34%)	⬇️
ibis/omniscidb/client.py	58.33% <0%> (-2.23%)	⬇️
ibis/common/geospatial.py	80.23% <0%> (-1.17%)	⬇️
... and 6 more

[xmnlab]

LGTM