[Feature Request] Use CDN to distribute MSI package

## Symptom

Azure CLI MSI package is delivered by an [Azure storage account](https://docs.microsoft.com/en-us/azure/storage/) located in [West US (California)](https://azure.microsoft.com/en-us/global-infrastructure/geographies/): https://azcliprod.blob.core.windows.net/msi/azure-cli-2.27.2.msi

Downloading Azure CLI MSI package is slow:

```
> curl.exe https://azcliprod.blob.core.windows.net/msi/azure-cli-2.27.2.msi -o out.msi
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 48.3M 100 48.3M 0 0 2752k 0 0:00:18 0:00:18 --:--:-- 1508k
```

## Proposal

We should use [Azure CDN](https://azure.microsoft.com/en-us/services/cdn/) to accelerate the MSI distribution.

Using Akamai CDN, the download speed can be significantly improved (14x faster):

```
> curl.exe https://azclicdn3.azureedge.net/msi/azure-cli-2.27.2.msi -o out.msi
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 48.3M 100 48.3M 0 0 24.1M 0 0:00:02 0:00:02 --:--:-- 21.3M
```

Notes: Tests are made with Microsoft corp net.