Need to remove redundant http://azurecliprod.blob.core.windows.net/edge/index.html

**Is your feature request related to a problem? Please describe.**

The [edge build](https://github.com/Azure/azure-cli#edge-builds) pipeline uses a custom index https://azurecliprod.blob.core.windows.net/edge

```
pip3 install --upgrade --pre azure-cli --extra-index-url https://azurecliprod.blob.core.windows.net/edge --no-cache-dir --upgrade-strategy=eager
```

According to [PEP 503](https://www.python.org/dev/peps/pep-0503/), the index should be available at http://azurecliprod.blob.core.windows.net/edge/ (✔), like https://pypi.org/simple/.

However, the edge build pipeline creates a redundant http://azurecliprod.blob.core.windows.net/edge/index.html (❌) which is not a valid index URL accepted by `pip`.

Moreover, even if we get http://azurecliprod.blob.core.windows.net/edge/ working, the contents inside it is not honored by `pip` at all (https://github.com/pypa/pip/issues/9399).

**Describe the solution you'd like**
1. Remove http://azurecliprod.blob.core.windows.net/edge/index.html from the edge build pipeline.
2. Use a valid index like http://azurecliprod.blob.core.windows.net/edge/ to obey PEP 503, even though it is not used by `pip`. Azure Storage Account also doesn't support root access on a container, so we need to use something like http://azurecliprod.blob.core.windows.net/edge/simple/
3. The beta build pipeline can't reuse https://azurecliprod.blob.core.windows.net/edge/azure-cli/ and must put `.whl` and `.tar.gz` files under https://azurecliprod.blob.core.windows.net/beta/azure-cli/