Implement casting/mapping towards datatype xsd:dateTime and xsd:date.

[realHannes]

This PR provides the implementation for request Issue #1819 @hannahbast .

xsd:date(?dateStr) and xsd:dateTime(?dateTimeStr) are now implemented as built-in function calls which enable variable value datatype-casting from xsd:string to xsd:dateTime (+ xsd:date ).

[codecov]

Codecov Report

Attention: Patch coverage is 98.13084% with 2 lines in your changes missing coverage. Please review.

Project coverage is 90.19%. Comparing base (8fe0642) to head (9d3009f).

Files with missing lines	Patch %	Lines
src/util/DateYearDuration.cpp	94.44%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1825      +/-   ##
==========================================
+ Coverage   90.18%   90.19%   +0.01%     
==========================================
  Files         400      400              
  Lines       38440    38501      +61     
  Branches     4306     4316      +10     
==========================================
+ Hits        34666    34725      +59     
- Misses       2479     2480       +1     
- Partials     1295     1296       +1     

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[joka921]

Thank you very much, that looks very nice.

[joka921]

Very nice, only two minor comments remaining

[sparql-conformance]

Conformance check passed ✅

No test result changes.

Details: https://qlever.cs.uni-freiburg.de/sparql-conformance-ui?cur=9d3009f0c0c8f1fbc33261372fcbd1b5e187e046&prev=8fe06428ee1dddbb3ebcb41a1d93525075571bc1

[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