Allow non-interactive install of az cli using script

**Is your feature request related to a problem? Please describe.**
I'm trying to install the az cli using the script approach (`curl -L https://aka.ms/InstallAzureCli | bash`) in an automated fashion. Unfortunately, the script prompts for a number of directories with no apparent way to provide those values via command line arguments or environment variables so the script can't run headless.

**Describe the solution you'd like**
Allow the INSTALL_DIR and BIN_DIR values to be provided either as command line arguments or environment variables.

Alternatively, if the CLI could be downloaded as a single binary instead of a python script that must be initialized that would be great.

**Describe alternatives you've considered**
Installing via a package manager is not viable in this case because 1) we don't have the necessary permissions on the system and 2) need to support a variety operating systems.

**Additional context**