Remove remaining usages of MinValue and clean up related code

[minichma]

Remove remaining usages of MinValue and clean up related code, i.e.

• Replace usage of DateTime.MinValue in RecurrencePatternEvaluator.
• Simplify RecurrencePatternSerializer.CheckMutuallyExclusive to avoid using reflection and checking for MinValue

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...alization/DataTypes/RecurrencePatternSerializer.cs	0%	0 Missing and 1 partial ⚠️

@@         Coverage Diff         @@
##           main   #668   +/-   ##
===================================
  Coverage    63%    63%           
===================================
  Files        99     99           
  Lines      4594   4586    -8     
  Branches   1085   1083    -2     
===================================
  Hits       2877   2877           
+ Misses     1258   1251    -7     
+ Partials    459    458    -1     

Files with missing lines	Coverage Δ
Ical.Net/Evaluation/RecurrencePatternEvaluator.cs	71% <100%> (ø)
...alization/DataTypes/RecurrencePatternSerializer.cs	70% <0%> (+2%)	⬆️

[axunonb]

Thanks for the missing parts