Update Sun-zenith reducer defaults

[ameraner]

This PR updates the Sun-zenith reducer default parameters to reduce the effect of the reduction and keep more data close to the terminator. See #2643 for the discussion.

• Closes SunZenithReducer defaults make True Color FCI imagery too dark at high solar zenith angles #2643
• Fully documented

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (ed220be) 95.21% compared to head (4dd1920) 95.21%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2653   +/-   ##
=======================================
  Coverage   95.21%   95.21%           
=======================================
  Files         356      356           
  Lines       51605    51605           
=======================================
  Hits        49134    49134           
  Misses       2471     2471           

Flag	Coverage Δ
behaviourtests	4.22% <50.00%> (ø)
unittests	95.83% <100.00%> (ø)

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[coveralls]

Pull Request Test Coverage Report for Build 7021329657

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 95.784%

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Totals
Change from base Build 7019457197:	0.0%
Covered Lines:	49260
Relevant Lines:	51428

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💛 - Coveralls

[mraspaud]

LGTM