Correctly print decimal datatype for CONSTRUCT if decimal point is not contained in literal

[RobinTF]

Fixes #2454 by printing the datatype instead of using the short hand notation for these cases.
This way queries like

CONSTRUCT {
  ?a a ""
}
WHERE {
  VALUES ?a { 960000.06 }
}

no longer turn the float into an integer. (Loss of precision is a related but different issue.)

[sparql-conformance]

Overview

Number of Tests	Passed ✅	Failed ❌	Intended ⚠️	Not tested
525	439	19	67	0

Conformance check passed ✅

No test result changes.

Details: https://qlever.dev/sparql-conformance-ui?cur=7a4b9f7014aafd28a19a252f3cc094b56bbbe62a&prev=a8c9d865aac01c673ffa3b56758a12dbb94f7676

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.09%. Comparing base (a8c9d86) to head (7a4b9f7).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2486   +/-   ##
=======================================
  Coverage   91.09%   91.09%           
=======================================
  Files         465      465           
  Lines       39690    39691    +1     
  Branches     5312     5313    +1     
=======================================
+ Hits        36155    36156    +1     
+ Misses       2020     2019    -1     
- Partials     1515     1516    +1     

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[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