Allow operations to not store their result in the cache

[joka921]

Each operation now has a bool that determines whether the results can be stored in the cache or not (whether it is actually stored depends on other circumstances, like the available cache size). That bool does not have to be fixed when the operation is created, but can be changed.

For example, this is useful for index scans that only return a subset of their full result (because of another constraining operation, like a join or a filter).

[codecov]

Codecov Report

Attention: Patch coverage is 90.90909% with 4 lines in your changes missing coverage. Please review.

Project coverage is 89.68%. Comparing base (ec806f0) to head (4064a85).
Report is 7 commits behind head on master.

Files with missing lines	Patch %	Lines
src/engine/Operation.cpp	93.10%	1 Missing and 1 partial ⚠️
src/util/ConcurrentCache.h	84.61%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1665      +/-   ##
==========================================
+ Coverage   89.58%   89.68%   +0.09%     
==========================================
  Files         381      383       +2     
  Lines       36813    36962     +149     
  Branches     4173     4178       +5     
==========================================
+ Hits        32978    33148     +170     
+ Misses       2523     2515       -8     
+ Partials     1312     1299      -13     

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[hannahbast]

1-1 with Johannes, looks great, some minor changes

[sparql-conformance]

Conformance check passed ✅

No test result changes.

Details: https://qlever.cs.uni-freiburg.de/sparql-conformance-ui?cur=4064a85ccf98cb56a3572fc4c57dcf1cdb21278b&prev=4a159948af0b56472898e34392754141c68e07cf

[hannahbast]

Great, I wrote a description and will merge this once all the checks are green

[sonarqubecloud]

Quality Gate passed

Issues
3 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