Merge command groups instead of overriding

[KaneFreeman]

Type: bug

The following has been addressed in the PR:

• [x] There is a related issue
• [x] All code has been formatted with prettier as per the readme code style guidelines
• [ ] Unit or Functional tests are included in the PR

Description: When the same command group is built in and installed, the commands should be merged instead of the built in command group overriding the installed.

Resolves #197

[codecov[bot]]

Codecov Report

Merging #268 into master will increase coverage by 0.01%. The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #268      +/-   ##
==========================================
+ Coverage   98.04%   98.06%   +0.01%     
==========================================
  Files          21       21              
  Lines         819      826       +7     
  Branches      133      134       +1     
==========================================
+ Hits          803      810       +7     
  Misses         16       16

Impacted Files	Coverage Δ
src/allCommands.ts	100% <100%> (ø)	:arrow_up:

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[agubler]

Can we get a unit test for this?

[KaneFreeman]

@agubler I have moved the combining code into a separate function and built a unit test for that function.