SF: Use consistent names for display IDs

There are two types of display IDs: hwc2_display_t for HWC IDs, and
int32_t for SF IDs. The latter are confusingly referred to as "hwcId".

This CL renames them to "hwcDisplayId" and "displayId", respectively.
Note that int32_t will be replaced by DisplayId in a follow-up CL.

Bug: 74619554
Test: Build
Change-Id: Ia9b621d385c2bf842a2093b578140dc7a2eaea69
diff --git a/services/surfaceflinger/tests/unittests/DisplayTransactionTest.cpp b/services/surfaceflinger/tests/unittests/DisplayTransactionTest.cpp
index 0b6a9b1..1a7805a 100644
--- a/services/surfaceflinger/tests/unittests/DisplayTransactionTest.cpp
+++ b/services/surfaceflinger/tests/unittests/DisplayTransactionTest.cpp
@@ -234,8 +234,8 @@
  *
  */
 
-template <DisplayDevice::DisplayType type, DisplayDevice::DisplayType hwcId, int width, int height,
-          Critical critical, Async async, Secure secure, int grallocUsage>
+template <DisplayDevice::DisplayType type, DisplayDevice::DisplayType displayId, int width,
+          int height, Critical critical, Async async, Secure secure, int grallocUsage>
 struct DisplayVariant {
     // The display width and height
     static constexpr int WIDTH = width;
@@ -245,7 +245,7 @@
 
     // The type for this display
     static constexpr DisplayDevice::DisplayType TYPE = type;
-    static constexpr DisplayDevice::DisplayType HWCOMPOSER_ID = hwcId;
+    static constexpr DisplayDevice::DisplayType DISPLAY_ID = displayId;
 
     // When creating native window surfaces for the framebuffer, whether those should be critical
     static constexpr Critical CRITICAL = critical;
@@ -257,7 +257,7 @@
     static constexpr Secure SECURE = secure;
 
     static auto makeFakeExistingDisplayInjector(DisplayTransactionTest* test) {
-        auto injector = FakeDisplayDeviceInjector(test->mFlinger, TYPE, HWCOMPOSER_ID);
+        auto injector = FakeDisplayDeviceInjector(test->mFlinger, TYPE, DISPLAY_ID);
         injector.setSecure(static_cast<bool>(SECURE));
         return injector;
     }