libbinder: RPC big 'session' rename

Before, 'connection' was used for a group of TCP connection. This
updates the names for most types to work with the following definitions:

- session - group of connections
- connection - a single tcp connection
- socket - only when referring to a socket being setup for a connection

Bug: N/A
Test: binderRpcTest, binderRpcBenchmark
Change-Id: If07afd9af680cd2a5ece6506df5383e5cc258663
diff --git a/libs/binder/Android.bp b/libs/binder/Android.bp
index 3f110c9..31227ab 100644
--- a/libs/binder/Android.bp
+++ b/libs/binder/Android.bp
@@ -115,7 +115,7 @@
         "PersistableBundle.cpp",
         "ProcessState.cpp",
         "RpcAddress.cpp",
-        "RpcConnection.cpp",
+        "RpcSession.cpp",
         "RpcServer.cpp",
         "RpcState.cpp",
         "Static.cpp",