Deprecate CompileStep.run. The problem with this function is that it
does the RunStep with the same build.zig context as the CompileStep, but
this is not desirable when running an executable that is provided by a
dependency package. Instead, users should use `b.addRunArtifact`.
This has the additional benefit of conforming to the existing naming
conventions.

Additionally, support enum literals in config header options values.