Store internal IRIs like `ql:has-predicate` in the normal vocabulary

[joka921]

So far, there was special code for internal IRIs like ql:has-predicate or ql:default-graph. Now there is special code only in the first stage of the indexing building, but once the partial vocabularies are merged, they have a name in the normal vocabulary just like all other entities. In particular, this fixes the problem that ql:default-graph was shown as 3 in the output.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 87.95181% with 10 lines in your changes missing coverage. Please review.

Project coverage is 89.50%. Comparing base (d900cd7) to head (79a91c9). Report is 5 commits behind head on master.

Files with missing lines	Patch %	Lines
src/engine/CountAvailablePredicates.cpp	0.00%	9 Missing :warning:
src/index/IndexBuilderTypes.h	95.23%	0 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1465 +/- ## ========================================== + Coverage 89.42% 89.50% +0.08% ========================================== Files 346 347 +1 Lines 25348 25552 +204 Branches 3385 3437 +52 ========================================== + Hits 22667 22870 +203 - Misses 1492 1496 +4 + Partials 1189 1186 -3 ```

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[sonarcloud[bot]]

Quality Gate passed

Issues
6 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 SonarCloud