[SBRP] Add packages for System.Text.Json 7.0.1 and its dependencies

[NikolaMilosavljevic]

We are currently allowing prebuilts in deployment-tools repo: https://github.com/dotnet/deployment-tools/blob/main/eng/SourceBuildPrebuiltBaseline.xml

    <UsagePattern IdentityGlob="System.Text.Json/7.0.1" />
    <UsagePattern IdentityGlob="Microsoft.Bcl.AsyncInterfaces/7.0.0" />
    <UsagePattern IdentityGlob="System.Text.Encodings.Web/7.0.0" />

We need to add SBRP packages, but only after we are able to add 7.0 targeting pack.

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[MichaelSimons]

This was added with dotnet/source-build-reference-packages#604.