add removceDuplicate helper method to VoiceCommand

[RHenigan]

Fixes #1664

This PR is ready for review.

Risk

This PR makes no API changes.

Testing Plan

• I have verified that I have not introduced new warnings in this PR (or explain why below)
• I have run the unit tests with this PR
• I have tested this PR against Core and verified behavior (if applicable, if not applicable, explain why below).
• I have tested Android, Java SE, and Java EE

Unit Tests

Added unit test for lists with duplicate strings

Core Tests

Test sending a list of voiceCommands where there are duplicate strings
You should now only see one voice command for each unique string you set

Core version / branch / commit hash / module tested against: Manticore
HMI name / version / branch / commit hash / module tested against: Manticore

Summary

This PR adds a helper function to VoiceCommand.java that will remove any duplicate strings when setVoiceCommands gets called. This PR adds the appropriate unit tests

CLA

• I have signed the CLA

[codecov]

Codecov Report

Merging #1665 (397536b) into develop (e1f9c02) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

❗ Current head 397536b differs from pull request most recent head fc8896d. Consider uploading reports for the commit fc8896d to get more accurate results

@@              Coverage Diff              @@
##             develop    #1665      +/-   ##
=============================================
- Coverage      53.99%   53.98%   -0.02%     
- Complexity      5304     5306       +2     
=============================================
  Files            555      555              
  Lines          24532    24533       +1     
  Branches        3094     3094              
=============================================
- Hits           13247    13245       -2     
  Misses         10134    10134              
- Partials        1151     1154       +3     

Impacted Files	Coverage Δ	Complexity Δ
...tdevicelink/managers/screen/menu/VoiceCommand.java	60.86% <100.00%> (+1.77%)	9.00 <2.00> (+1.00)
...smartdevicelink/encoder/VirtualDisplayEncoder.java	43.70% <0.00%> (-1.40%)	9.00% <0.00%> (ø%)
...ink/managers/screen/BaseTextAndGraphicManager.java	64.16% <0.00%> (+0.41%)	52.00% <0.00%> (+2.00%)