TINKERPOP-3083: The split() step should provide a way to split an entire string

[andreachild]

https://issues.apache.org/jira/browse/TINKERPOP-3083

Changed split() local and global steps to parse a string into individual characters if the separator is an empty string - previous implementation left the string intact. Introduced StringUtil utility class to reuse logic between the global and local step classes. Feature tests were executed using -DskipIntegrationTests=false and manual testing was executed using gremlin console with and without remote context.

Changelog entry to add when we have a designated section for it:

• Modified the split() step to split a string into a list of its characters if the given separator is an empty string.

Upgrade doc to add when we have a designated section for it:

==== Splitting a string into characters using split()
The `split()` step will now split a string into a list of its characters if the given separator is an empty string.
[source,groovy]
----
// previous implementation
g.inject("Hello").split("")
==>[Hello]
// new implementation
g.inject("Hello").split("")
==>[H,e,l,l,o]
----
See: link:https://issues.apache.org/jira/browse/TINKERPOP-3083[TINKERPOP-3083]

This is a back port from master branch which is at version 4.0. Original PR: apache#2741

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

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Additional details and impacted files

@@               Coverage Diff               @@
##             4.0-backport      #98   +/-   ##
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  Coverage                ?   76.37%           
  Complexity              ?    13238           
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  Files                   ?     1062           
  Lines                   ?    61574           
  Branches                ?     7344           
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  Hits                    ?    47025           
  Misses                  ?    12029           
  Partials                ?     2520           

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[Cole-Greer]

Nit: CHANGELOG. Otherwise LGTM

[andreachild]

Nit: CHANGELOG. Otherwise LGTM
Changelog should be added to the official branch at a later point as there is no section for 3.8 yet.

[andreachild]

Closing and will reopen new PR against 3.8-dev