Extend and rework IRF interpolation docs

[RuneDominik]

I tried to produce a more comprehensive version of the interpolation docs, especially the interpolation main-page. Suggestions very welcome.

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (12a6095) 94.84% compared to head (59b9408) 94.84%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #255   +/-   ##
=======================================
  Coverage   94.84%   94.84%           
=======================================
  Files          60       60           
  Lines        3083     3083           
=======================================
  Hits         2924     2924           
  Misses        159      159           

Files Changed	Coverage Δ
pyirf/interpolation/griddata_interpolator.py	100.00% <ø> (ø)
pyirf/interpolation/nearest_neighbor_searcher.py	100.00% <ø> (ø)
pyirf/interpolation/utils.py	97.61% <ø> (ø)
pyirf/interpolation/base_extrapolators.py	100.00% <100.00%> (ø)
pyirf/interpolation/component_estimators.py	99.27% <100.00%> (ø)
pyirf/interpolation/moment_morph_interpolator.py	100.00% <100.00%> (ø)
...yirf/interpolation/nearest_simplex_extrapolator.py	100.00% <100.00%> (ø)
pyirf/interpolation/quantile_interpolator.py	98.24% <100.00%> (ø)

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