Create Linux build images for .NET 11

[jkotas]

• Update to clang 21 (for now, we will want to update to clang 22 once it becomes available)
• Update eng/pipelines/common/templates/pipeline-with-resources.yml to use net11.0 images

[jkotas]

@sbomer Could you please take care of this when you get a chance?

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[am11]

@sbomer, bot has the hashes sorted out https://github.com/am11/dotnet-buildtools-prereqs-docker/pull/17/files, but I guess we want to fork net10.0 dir for net11.0 first?

[sbomer]

@am11 we merged the net11.0 images in dotnet/dotnet-buildtools-prereqs-docker#1499, mind pointing your bot to these?

[akoeplinger]

This was done via dotnet/dotnet-buildtools-prereqs-docker#1516 and #120775