{Core} Aladdin recommendation improvements

[houk-ms]

Description

This PR provides two improvements for Aladdin recommendation

1. When users input duplicated parameters, we take only a distinct set of parameters and send them to Aladdin service.

For example, when user inputs az group create -g rg1 -g rg2 -g rg3, the parameters we send to Aladdin is [--resource-group], not [--resource-group, --resource-group, --resource-group] . Otherwise, aladdin service may throw Query Too Long error.

Even for the cases where multiple same parameters may make sense, the change won't affect the recommendation result.

2. Handle the cases where descriptions may not be provided for sample commands in help.py

Otherwise, the recommendation will just fail.

Testing Guide

History Notes

[Component Name 1] BREAKING CHANGE: az command a: Make some customer-facing breaking change.
[Component Name 2] az command b: Add some customer-facing feature.

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[houk-ms]

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