Add RuleBuilder helper functions for built and prebuilt tools

Replace the common pattern of:
cmd.Tool(ctx.Config().HostToolPath(ctx, "tool"))
with:
cmd.BuiltTool("tool")

And similarly for PrebuiltBuildTool.

Test: m checkbuild
Change-Id: I7d63188505362c7df6a3b3e7330b4a2cca5a2409