Use online checksums for .NET Monitor Dockerfiles

[lbussell]

This is part of #6548. Instead of using hard-coded checksums, they should be downloaded from the build/release storage account. This makes the Dockerfiles more flexible and simplifies this repo's maintenance, since we will no longer need to calculate or keep track of checksums.

Example:

dotnet-docker/src/runtime/10.0/alpine3.22/amd64/Dockerfile

Lines 7 to 16 in 157267f

	RUN dotnet_version=10.0.0-preview.6.25358.103 \
	&& wget \
	https://builds.dotnet.microsoft.com/dotnet/Runtime/$dotnet_version/dotnet-runtime-$dotnet_version-linux-musl-x64.tar.gz \
	https://builds.dotnet.microsoft.com/dotnet/Runtime/$dotnet_version/dotnet-runtime-$dotnet_version-linux-musl-x64.tar.gz.sha512 \
	&& sha512sum -c dotnet-runtime-$dotnet_version-linux-musl-x64.tar.gz.sha512 \
	&& mkdir --parents /dotnet \
	&& tar --gzip --extract --no-same-owner --file dotnet-runtime-$dotnet_version-linux-musl-x64.tar.gz --directory /dotnet \
	&& rm \
	dotnet-runtime-$dotnet_version-linux-musl-x64.tar.gz \
	dotnet-runtime-$dotnet_version-linux-musl-x64.tar.gz.sha512

[lbussell]

CI build checksums are under ci.dot.net as expected:

https://ci.dot.net/public/diagnostics/monitor/9.1.0-preview.3.25363.1/dotnet-monitor-base-9.1.0-preview.3.25363.1-linux-x64.tar.gz
https://ci.dot.net/public-checksums/diagnostics/monitor/9.1.0-preview.3.25363.1/dotnet-monitor-base-9.1.0-preview.3.25363.1-linux-x64.tar.gz.sha512

Official builds are located in dotnetclichecksums storage account:

https://builds.dotnet.microsoft.com/dotnet-checksums/diagnostics/monitor/8.1.1/dotnet-monitor-base-8.1.1-linux-x64.tar.gz
https://dotnetclichecksums.blob.core.windows.net/dotnet/diagnostics/monitor/8.1.1/dotnet-monitor-base-8.1.1-linux-arm64.tar.gz.sha512

I filed dotnet/dotnet-monitor#8436 to track publishing these to dotnetcli (which maps to builds.dotnet.microsoft.com).