Having two packages in the same directory makes it harder for go tools
to understande the directory structure.
For example, in build/soong, "go test ./cc/..." fails with cyclic
package imports.
Bug: n/a
Test: go test ./cc/... (in build/soong)
Change-Id: I7a040bf30b1e001680dd43fed9747e9651372274
Give prebuilt_etc and sh_binary their own packages and split the
gigantic main Android.bp up to small, per-package ones.
Test: m nothing, TreeHugger
Bug: 156980228
Change-Id: I7b00cd344b9f16861f1ff39edf0029f016b853d0