InputMapper refactor: Change readerconfig pointer to const ref

We are refactoring Input-mapper to ensure they are configured at the
time of initialisation.

In this CL we are changing InputReaderConfiguration raw pointer to
a const reference and rename it to readerConfig for clarity.

Test: build, inputflinger_tests, presubmit checks

Bug: 256009910
Change-Id: Iae22c8cfba836bd311a51fca13d680456a61e604
diff --git a/services/inputflinger/reader/mapper/ExternalStylusInputMapper.cpp b/services/inputflinger/reader/mapper/ExternalStylusInputMapper.cpp
index c5a3075..bbb641e 100644
--- a/services/inputflinger/reader/mapper/ExternalStylusInputMapper.cpp
+++ b/services/inputflinger/reader/mapper/ExternalStylusInputMapper.cpp
@@ -47,7 +47,7 @@
 }
 
 std::list<NotifyArgs> ExternalStylusInputMapper::reconfigure(nsecs_t when,
-                                                             const InputReaderConfiguration* config,
+                                                             const InputReaderConfiguration& config,
                                                              uint32_t changes) {
     getAbsoluteAxisInfo(ABS_PRESSURE, &mRawPressureAxis);
     mTouchButtonAccumulator.configure();