Document Sentry CLI MSBuild parameters when building in a docker container

[mattjohnsonpint]

Problem Statement

Our docs here:
https://docs.sentry.io/platforms/dotnet/configuration/msbuild/

... assume you are building the project without Docker. If you are building with Docker, then there are some gotchas that should be documented.

Solution Brainstorm

Specifically, we need to show:

• Passing the SENTRY_AUTH_TOKEN via docker build, then importing it with ARG and using it with ENV in the dockerfile.
• In a multistage dockerfile with separate stages for dotnet build and dotnet publish, we should pass -p:UseSentryCLI=false in the publish stage, so that Sentry CLI is only used during the build stage.

[mattjohnsonpint]

A working example is in comments here:

#2406 (comment)

[bitsandfoxes]

This sounds like it could have prevented #3056