Two helper ranges to simplify the rewriting of co-routines to C++17

[joka921]

This introduces CachingTransformInputRange and CachingContinuableTransformInputRange, two abstractions that will make the porting from C++20 generators to C++17 easier.

CachingTransformInputRange is similar to ranges::transform, but caches the intermediate results by value and always is an InputRange. This is closer to the behavior of coroutines than ranges::transform which in particular recomputes the transformation if the same iterator is dereferenced multiple times.

CachingContinuableTransformInputRange in addition has special return values for the transformation which can control the iteration, e.g. Continue (skip the current element).

[codecov]

Codecov Report

Attention: Patch coverage is 93.22034% with 4 lines in your changes missing coverage. Please review.

Project coverage is 90.61%. Comparing base (8444a5e) to head (b8d4057).
Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
src/util/InputRangeUtils.h	92.98%	0 Missing and 4 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1892      +/-   ##
==========================================
+ Coverage   90.58%   90.61%   +0.02%     
==========================================
  Files         413      414       +1     
  Lines       40041    40100      +59     
  Branches     4528     4536       +8     
==========================================
+ Hits        36272    36335      +63     
+ Misses       2420     2416       -4     
  Partials     1349     1349              

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[hannahbast]

1-1 with Johannes, impressive stuff (easy to use by example, but not so easy to understand in depth and to design in the first place)

[hannahbast]

Round 2 with Johannes, looks great

[hannahbast]

Looks good now, when the tests runs through, I will make another quick pass, write a description and merge it

[sparql-conformance]

Conformance check passed ✅

No test result changes.

Details: https://qlever.cs.uni-freiburg.de/sparql-conformance-ui?cur=b8d405732e47a0c47a25a8ab865647230b09f133&prev=8444a5e3fc876d30c4601b27217e7c9343d641dd

[sonarqubecloud]

Quality Gate passed

Issues
2 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