allow run-as to carry unix_stream_sockets

Allow run-as to transmit unix_stream_sockets from the shell user to
Android apps. This is needed for Android Studio's profiling tool to
allow communcation between apps and debugging tools which run as the
shell user.

Bug: 35672396
Test: Functionality was tested by shukang
Test: policy compiles.
Change-Id: I2cc2e4cd5b9071cbc7d6f6b5b0b71595fecb455e

public/runas.te

@@ -4,6 +4,7 @@ type runas_exec, exec_type, file_type;
 allow runas adbd:process sigchld;
 allow runas shell:fd use;
 allow runas shell:fifo_file { read write };
+allow runas shell:unix_stream_socket { read write };
 allow runas devpts:chr_file { read write ioctl };
 allow runas shell_data_file:file { read write };