Detect if more than one version of Core Tools is installed

With multiple installers per platform (on Windows, we have MSI, npm, choco, dotnet tool), it's quite easy for customers to install Core Tools with one installer, then forget how they installed it and might end up using a separate installer to update Core Tools. This leads to confusion as a newly installed version of Core Tools might not be the one being used because another version is earlier in the PATH.

Can our installers run a check on the PATH and warn if there are more than 1 copy of Core Tools found?

Review the installer entry points for MSI, npm, choco, and dotnet tool across the repository, then trace how each can inspect PATH. Done means installers warn when more than one Core Tools copy is found, covering the supported platforms and installer paths described in the issue.

Written by the indexing model from the issue text.