Maintain parsed aliases for commands over using yargs internal

[agubler]

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
• [x] Unit or Functional tests are included in the PR

Description:

Parsed aliases are only available from yargs when running a command with a group and name - Therefore running a default command such as dojo test throws an error because there is no aliases object.

This change moves from using an internally yargs generated and maintained aliases map, to explicitly maintaining an equivalent map in dojo/cli. This means that command line options saved in the dojorc config will work for default commands, aliased commands and regular commands.

Resolves #221

[codecov[bot]]

Codecov Report

Merging #222 into master will decrease coverage by 0.02%. The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #222      +/-   ##
==========================================
- Coverage   95.06%   95.04%   -0.03%     
==========================================
  Files          19       19              
  Lines         507      525      +18     
  Branches       69       70       +1     
==========================================
+ Hits          482      499      +17     
  Misses         13       13              
- Partials       12       13       +1

Impacted Files	Coverage Δ
src/registerCommands.ts	99.02% <100%> (-0.98%)	:arrow_down:

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