Remove libcompos_client

CompOS APEX no longer needs to provide libcompos_client API (added
recently during T development).

Some of the code is still reusable, so the remaining code is moved to
composd/src/fd_server_helper.rs.

Bug: 205750213
Test: m
Test: atest ComposHostTestCases

Change-Id: I584b700c41ffc0e08c6ac6c171cb17ab21c7d8ff
diff --git a/compos/apex/Android.bp b/compos/apex/Android.bp
index 36e3c3e..c68899a 100644
--- a/compos/apex/Android.bp
+++ b/compos/apex/Android.bp
@@ -45,16 +45,12 @@
         "compos_verify_key",
         "composd",
         "composd_cmd",
-        "pvm_exec", // to be superseded by libcompos_client
+        "pvm_exec", // deprecated
 
         // Used in VM
         "compsvc",
     ],
 
-    native_shared_libs: [
-        "libcompos_client",
-    ],
-
     apps: [
         "CompOSPayloadApp",
     ],