[Demo] Allow specifying a custom access token

[jiasli]

Description

Allow specifying a custom access token by monkey-patching azure.cli.core._profile.Profile.get_login_credentials.

Testing Guide

# With --access-token
> az group show -n fy --subscription 0b1f6471-1bf0-4dda-aec3-cb9272f09590 --access-token "eyJ0eXAiO..."
Subscription '0b1f6471-1bf0-4dda-aec3-cb9272f09590' not recognized.
Using the provided access token.
{
  "id": "/subscriptions/0b1f6471-1bf0-4dda-aec3-cb9272f09590/resourceGroups/fy",
  "location": "westus",
  "managedBy": null,
  "name": "fy",
  "properties": {
    "provisioningState": "Succeeded"
  },
  "tags": null,
  "type": "Microsoft.Resources/resourceGroups"
}

# Without --access-token
> az group show -n fy
Using the credential from `az login`.
{
  "id": "/subscriptions/0b1f6471-1bf0-4dda-aec3-cb9272f09590/resourceGroups/fy",
  "location": "westus",
  "managedBy": null,
  "name": "fy",
  "properties": {
    "provisioningState": "Succeeded"
  },
  "tags": null,
  "type": "Microsoft.Resources/resourceGroups"
}

Note that this warning

Subscription '0b1f6471-1bf0-4dda-aec3-cb9272f09590' not recognized.

can't be disabled by monkey-patching because it is printed before the command reaches get_resource_group. To hide it, use --only-show-errors.