GH-610 add PipedCopyIteratorUnordered and AsyncIteratorFetcherUnordered

[hmottestad]

Issue resolved (if any): #610

Description of this pull request:

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Please check all the lines before posting the pull request:

• I've created tests for all my changes
• My pull request isn't fixing or changing multiple unlinked elements (please create one pull request for each element)
• I've applied the code formatter (mvn formatter:format on the backend, npm run format on the frontend) before posting my pull request, mvn formatter:validate to validate the formatting on the backend, npm run validate on the frontend
• All my commits have relevant names
• I've squashed my commits (if necessary)

[hmottestad]

export JAVA_OPTIONS="-Xmx32G"
./rdf2hdt.sh -multithread -disk -disklocation "../disk-temp/" ../../latest-lexemes.nt.gz ../../latest-lexemes.hdt

Before

[main] . [##########] 100.0 done
File converted in ..... 10 min 33 sec 853 ms 834 us
Total Triples ......... 179203844
Different subjects .... 25554000
Different predicates .. 2337
Different objects ..... 42155144
Common Subject/Object . 24163053

After

[main] . [##########] 100.0 done
File converted in ..... 8 min 11 sec 92 ms 917 us
Total Triples ......... 179203844
Different subjects .... 25554000
Different predicates .. 2337
Different objects ..... 42155144
Common Subject/Object . 24163053