Publish prebuilt reports for each repo

[Winniexu01]

Fixes dotnet/source-build#4160

Store the prebuilt repots for each repo as pipeline artifacts rather than the overall build's prebuilt report, which will make investigations of prebuilt go more quickly.

I introduced a new property DotNetBuildPrebuiltReportDir which point to artifacts\prebuilt-report\<reponame>\, all repo's prebuilt reports will respect this property and move to that folder.

[mthalman]

@Winniexu01 - Is there an example build containing a prebuilt that you can provide which demonstrates this new behavior?

[Winniexu01]

@mthalman Example build: https://dev.azure.com/dnceng/internal/_build/results?buildId=2536531&view=results (internal Microsoft link)

[mthalman]

@mthalman Example build: https://dev.azure.com/dnceng/internal/_build/results?buildId=2536531&view=results (internal Microsoft link)

I was looking for a build that had prebuilts being reported in order to validate the placement of files in the pipeline artifacts. This build doesn't seem to have any prebuilts.

[Winniexu01]

Hi @mthalman Here is new build (internal Microsoft link) that CentOS9 failed with '3 Prebuilt Exist'.