Docker C# improvements - explore use of Chieseled containers

[angrave]

Chiseled containers have no shell, no install and don't run apps as root

https://github.com/dotnet/dotnet-docker/blob/main/documentation/ubuntu-chiseled.md
https://github.com/dotnet/dotnet-docker/blob/main/documentation/image-variants.md

for webapi and maybe taskengine.
Note taskengine needs a shell to execute llamafile; so we would want to put the shell back in, and install the other packages needed to SpeechSDK.

Test on AMD64 and ARM64 (new Apple Macs)