{Version} Only show az upgrade instruction when update for azure-cli is available

[fengzhou-msft]

Description

Make the instruction of using az upgrade only displayed when there is update for azure-cli package to prevent issues like #15133.

This PR also deprecates the _update_latest_from_pypi method which uses fuzzy match in package name and package description to search for azure-cli in pypi. Lots of packages that contain azure-cli in name or in description are returned. So this method is slow. This PR replaces it with _update_latest_from_github which searches for the latest versions on Github master branch. Legacy module packages installed before such as azure-cli-vm will no longer be listed in az --version.

Comparison of azdev perf benchmark "az --version" --runs 10:
Before:

[
  {
    "Avg": 3.8947,
    "Command": "az --version",
    "Max": 4.4901,
    "Media": 4.3117,
    "Min": 2.0803,
    "Runs": 10,
    "Std": 0.9021
  }
]

After:

[
  {
    "Avg": 3.4807,
    "Command": "az --version",
    "Max": 3.9086,
    "Media": 3.8219,
    "Min": 2.0002,
    "Runs": 10,
    "Std": 0.7321
  }
]

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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