Reland "Rename SIGNALING and WORKER to PRIMARY and SECONDARY"

This is a reland of a37f2bd9421868e222d591d3371486a6ab939fd6

Original change's description:
> Rename SIGNALING and WORKER to PRIMARY and SECONDARY
>
> This makes the proxy macros less confusing when the secondary thread
> is sometimes the worker thread, sometimes the networking thread.
>
> Bug: none
> Change-Id: I1a8cebb82d09be44fe40e80c861bcfb47b9928e8
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/208763
> Reviewed-by: Tommi <tommi@webrtc.org>
> Commit-Queue: Harald Alvestrand <hta@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#33346}

Bug: none
Change-Id: If46a6679ac0fc947797dd7be87626ef7702faca2
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/208845
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Niels Moller <nisse@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Tommi <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33349}
diff --git a/pc/proxy_unittest.cc b/pc/proxy_unittest.cc
index 500828a..fdc7dc3 100644
--- a/pc/proxy_unittest.cc
+++ b/pc/proxy_unittest.cc
@@ -64,20 +64,20 @@
 
 // Proxies for the test interface.
 BEGIN_PROXY_MAP(Fake)
-PROXY_WORKER_THREAD_DESTRUCTOR()
+PROXY_SECONDARY_THREAD_DESTRUCTOR()
 PROXY_METHOD0(void, VoidMethod0)
 PROXY_METHOD0(std::string, Method0)
 PROXY_CONSTMETHOD0(std::string, ConstMethod0)
-PROXY_WORKER_METHOD1(std::string, Method1, std::string)
+PROXY_SECONDARY_METHOD1(std::string, Method1, std::string)
 PROXY_CONSTMETHOD1(std::string, ConstMethod1, std::string)
-PROXY_WORKER_METHOD2(std::string, Method2, std::string, std::string)
+PROXY_SECONDARY_METHOD2(std::string, Method2, std::string, std::string)
 END_PROXY_MAP()
 
 // Preprocessor hack to get a proxy class a name different than FakeProxy.
 #define FakeProxy FakeSignalingProxy
 #define FakeProxyWithInternal FakeSignalingProxyWithInternal
-BEGIN_SIGNALING_PROXY_MAP(Fake)
-PROXY_SIGNALING_THREAD_DESTRUCTOR()
+BEGIN_PRIMARY_PROXY_MAP(Fake)
+PROXY_PRIMARY_THREAD_DESTRUCTOR()
 PROXY_METHOD0(void, VoidMethod0)
 PROXY_METHOD0(std::string, Method0)
 PROXY_CONSTMETHOD0(std::string, ConstMethod0)
@@ -270,7 +270,7 @@
 };
 
 BEGIN_OWNED_PROXY_MAP(Foo)
-PROXY_SIGNALING_THREAD_DESTRUCTOR()
+PROXY_PRIMARY_THREAD_DESTRUCTOR()
 PROXY_METHOD0(void, Bar)
 END_PROXY_MAP()