Prepare the actual execution of UPDATE requests

[Qup42]

Add some helper functions that can and will be used to convert A QueryExecutionTree and the parsed representation of an update clause into the format, that the DeltaTriples expect.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 89.15%. Comparing base (7bd2438) to head (976ea93). Report is 7 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1592 +/- ## ========================================== + Coverage 89.10% 89.15% +0.05% ========================================== Files 371 372 +1 Lines 34461 34572 +111 Branches 3899 3911 +12 ========================================== + Hits 30705 30824 +119 + Misses 2480 2471 -9 - Partials 1276 1277 +1 ```

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[Qup42]

To be able to properly test ExecuteUpdate::executeUpdate we need ParsedQuerys of Updates. This requires that Updates are not rejected by the visitor, but instead the server rejects Updates. I'll do that in the following commits but we can also extract that to a separate PR.

[sparql-conformance[bot]]

Conformance check passed ✅

No test result changes.

Details: https://qlever.cs.uni-freiburg.de/sparql-conformance-ui?cur=976ea93632e35de6e15fe33ed6629fb70b6067bf&prev=f1490771f7a70d49bc1d3d08a95e31488aaa505e

[sonarcloud[bot]]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

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

See analysis details on SonarCloud