Remove sources from SDKs packages which are used for debugging

VS4M implements support for sourcelink in 16.3 - https://devdiv.visualstudio.com/DevDiv/_workitems/edit/695466. That should allow us to build debug symbols for SDKs packages without local sources dependency.

/cc @steveisok @akoeplinger

Tasks:

• Remove XI pathmap so we get the correct path in the .pdb (which is mapped via sourcelink): https://github.com/mono/mono/blob/807e4b3d6f24118302bbb5663f66a607d30f3a13/scripts/ci/run-jenkins.sh#L191-L192
• Remove XM pathmap so we get the correct path in the .pdb (which is mapped via sourcelink): https://github.com/mono/mono/blob/807e4b3d6f24118302bbb5663f66a607d30f3a13/scripts/ci/run-jenkins.sh#L245-L246
• Remove the sources from sdk archive, except stuff like linker which is still built from source in products