Add support for managed identity for redis

[twsouthwick]

This change does the following:

• Adds a new application module for the redis resource which handles adding the passwordless connection string to the app configuration
• Updates to a newer redis bicep module that allows using entra
• Adds a parameter to add entra users to the redis service
• Refactors the registration of the redis distributed cache to use managed identity

[twsouthwick]

I validated that this doesn't need any docs changes (couldn't find reference to the password/connection string/etc) and the demo continues to work as documented.

This should close https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1881951

[KSchlobohm]

@twsouthwick

It looks like this PR modifies the Startup.cs that is presented in the docs. Specifically, the changes regarding the new TokenCredential class that change the following sections.

• https://learn.microsoft.com/en-us/azure/architecture/web-apps/guides/reliable-web-app/dotnet/apply-pattern#use-defaultazurecredential-to-set-up-code
• https://learn.microsoft.com/en-us/azure/architecture/web-apps/guides/reliable-web-app/dotnet/apply-pattern#use-the-cache-aside-pattern

[twsouthwick]

Thanks @KSchlobohm - missed that part of the docs. I created a branch here https://github.com/twsouthwick/architecture-center/tree/rwa-servicing to update docs and will open a pr there when we're ready to merge here