Improve example validation and corrections

[ashovlin]

Issue #, if available: Backport of #10101 to CLIv1

Description of changes:

This improves the validation we do in the existing tests/functional/docs/test_examples.py. Previously we were only testing the service and operation name.

Now, it runs the example commands through the appropriate parser for each. This will catch more issues: invalid syntax, invalid argument names, missing required parameters.

This also fixes the examples that fail for the updated test.

Note: I did not address examples that specify --cli-input-json/etc., it'll require more work to parse and validate those.

Note: The one file difference is application-autoscaling/put-scaling-policy - it was already correct in v1.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.43%. Comparing base (c4681b5) to head (d4b8c11).
⚠️ Report is 357 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop   #10266      +/-   ##
===========================================
+ Coverage    93.39%   93.43%   +0.04%     
===========================================
  Files          210      211       +1     
  Lines        17052    17283     +231     
===========================================
+ Hits         15925    16149     +224     
- Misses        1127     1134       +7     

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[ashovlin]

Rebased on develop via https://github.com/aws/aws-cli/compare/097d180e7d7951511ff3ab72bd61659a9d5cfaef..d4b8c11df4d26a78f87a90596902e1ba43dc1cc7, CI was failing due to the recent 3.9 drop.