Move ApiDocs.bp and StubLibraries.bp to api dir

Make a symlink from api/docs -> docs, since many places are
hardcoding the path fw/base/docs.

Bug: 271563074
Test: presubmit
Change-Id: I354f3cb62535f34d8819d158e53aa46ff26dc18a

Android.bp

@@ -612,8 +612,6 @@ stubs_defaults {
 }
 
 build = [
-    "StubLibraries.bp",
-    "ApiDocs.bp",
     "ProtoLibraries.bp",
     "TestProtoLibraries.bp",
 ]

api/Android.bp

@@ -252,3 +252,8 @@ java_genrule {
     out: ["api_fingerprint.txt"],
     cmd: "cat $(in) | md5sum | cut -d' ' -f1 > $(out)",
 }
+
+build = [
+    "ApiDocs.bp",
+    "StubLibraries.bp",
+]

api/docs

@@ -0,0 +1 @@
+../docs