Extract utility class to iterate over terms docs [LUCENE-8608]

[asfimport]

Today we re-implement the same algorithm in various places
when we want to consume all docs for a set/list of terms. This
caused serious slowdowns for instance in the case of applying
updates fixed in #9648. This change extracts the common
usage and shares the interation code including logic to reuse
Terms and PostingsEnum instances as much as possble and adds
tests for it.

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Migrated from LUCENE-8608 by Simon Willnauer (@s1monw), resolved Dec 13 2018
Pull requests: apache/lucene-solr#526

[asfimport]

ASF subversion and git services (migrated from JIRA)

Commit 4272c63 in lucene-solr's branch refs/heads/master from @s1monw
https://git-wip-us.apache.org/repos/asf?p=lucene-solr.git;h=4272c63

LUCENE-8608: Extract utility class to iterate over terms docs

Today we re-implement the same algorithm in various places
when we want to consume all docs for a set/list of terms. This
caused serious slowdowns for instance in the case of applying
updates fixed in #9648. This change extracts the common
usage and shares the interation code including logic to reuse
Terms and PostingsEnum instances as much as possble and adds
tests for it.

[asfimport]

ASF subversion and git services (migrated from JIRA)

Commit 8f4e4a4 in lucene-solr's branch refs/heads/branch_7x from @s1monw
https://git-wip-us.apache.org/repos/asf?p=lucene-solr.git;h=8f4e4a4

LUCENE-8608: Extract utility class to iterate over terms docs

Today we re-implement the same algorithm in various places
when we want to consume all docs for a set/list of terms. This
caused serious slowdowns for instance in the case of applying
updates fixed in #9648. This change extracts the common
usage and shares the interation code including logic to reuse
Terms and PostingsEnum instances as much as possble and adds
tests for it.