Write raw files to disk instead of the ninja file

Writing raw files as rules in the ninja file unnecessarily bloats
the ninja file.  Write files immediately to disk instead to files
based on the hash of the contents, and then emit ninja rules to
copy the files into place during the build.  Delete obsolete files
in a singleton at the end of analysis.

Bug: 306029038
Test: Run: m libc_musl_version.h
           touch build/soong/Android.bp
           m libc_musl_version.h
      libc_musl_version.h/genrule.sbox.textproto is not recopied.
Test: Run: lunch aosp_cf_x86_64_phone-userdebug
           m libc_musl_version.h
	   lunch aosp_x86_64-userdebug
	   m libc_musl_version.h
	   lunch aosp_cf_x86_64_phone-userdebug
	   m libc_musl_version.h
      libc_musl_version.h/genrule.sbox.textproto is recopied but restat prevents rerunning the genrule.
Test: Run: touch out/soong/raw-aosp_cf_x86_64_phone/00/foo
           touch build/soong/Android.bp
	   m nothing
      out/soong/raw-aosp_cf_x86_64_phone/00/foo is removed.
Change-Id: I172869c4d49565504794c051e2e8c1f7cf46486e