Install PowerShell from Azure Linux repo

[mthalman]

There are several instances of Azure Linux / CBL Mariner Dockerfiles installing PowerShell from PMC:

dotnet-buildtools-prereqs-docker/src/azurelinux/3.0/net9.0/crossdeps/amd64/Dockerfile

Lines 31 to 42 in 9a84524

	# Powershell and azure cli aren't currently part of the azure linux 3.0 repositories.
	# Install powershell from the rhel8 MS repo, and azure-cli using PIP
	# Install powershell from the Microsoft repository.
	RUN curl -sSL -O https://packages.microsoft.com/config/rhel/8/packages-microsoft-prod.rpm && \
	rpm -i packages-microsoft-prod.rpm && \
	rm -f packages-microsoft-prod.rpm && \
	tdnf update -y && \
	tdnf install -y --setopt tsflags=nodocs \
	powershell && \
	rm /etc/yum.repos.d/microsoft-prod.repo && \
	tdnf clean all

These can be updated to simply install from the official Azure Linux repo. In other words, this works:

docker run --rm mcr.microsoft.com/azurelinux/base/core:3.0 tdnf install -y powershell