Use bazel rules to simplify build scripts

[djungelorm]

A lot of the custom build scripts in tools/build/... can probably be replaced by using rules provided by bazel, including:

• bazel_skylib
• https://github.com/bazelbuild/rules_dotnet
• https://github.com/bazelbuild/rules_python

This would remove a lot of custom logic and code on our end, instead relying on rules maintained by the bazel developers/community. This will also help with getting the bazel build working on Windows, as these rules are cross platform.

[djungelorm]

krpc2 repository now uses rules_dotnet and should be buildable using Bazel on both Linux and Windows. We can do similar here.