Add support for cliArgumentName in the member metadata

[dstufft]

Adds a member value cliArgumentName that can be used to override what the automatically generated name on the CLI is.

This includes validation that the property is of the right type (although I decided not to try to validate that the cliArgumentName doesn't exist anywhere else, because I didn't see a great way of doing that besides validating the entire schema of a service model (and even then, it would block that name from being used as a member name itself, or a model name).

The tests also include validation that the cliArgumentName given does not collide with any other members on the same model, it contains the original argument name, and that within a single service, the same cliArgumentName is used for the same original name consistently (so that you don't have Region being renamed to --foo-region in one command, and --bar-region in another command for the same service).

[codecov-io]

Codecov Report

Merging #1424 into develop will decrease coverage by 0.02%. The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop    #1424      +/-   ##
===========================================
- Coverage    81.21%   81.18%   -0.03%     
===========================================
  Files           88       88              
  Lines        12450    12450              
===========================================
- Hits         10111    10108       -3     
- Misses        2339     2342       +3

Impacted Files	Coverage Δ
botocore/model.py	97.61% <ø> (ø)	:arrow_up:
botocore/credentials.py	98.4% <0%> (-0.4%)	:arrow_down:

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[github-actions[bot]]

Greetings! It looks like this issue hasn’t been active in longer than one year. We encourage you to check if this is still an issue in the latest release. Because it has been longer than one year since the last update on this, and in the absence of more information, we will be closing this issue soon. If you find that this is still a problem, please feel free to provide a comment to prevent automatic closure, or if the issue is already closed, please feel free to reopen it.

[tim-finnigan]

After reviewing with the CLI team we decided to close this but may revisit it in the future.