Libbinder APIs are guarded

The following API was added for the API level 30 and beyond.  Currently,
its existence is tested using the null check which is done regardless of
the min sdk version of the compilation unit. (which in turn required us
to mark the API symbol weak regardless of the min sdk version.)

API 30:
* AStatus_getDescription
* AIBinder_Class_setHandleShellCommand

API 31:
* AParcel_getDataSize
* AParcel_reset
* AParcel_appendFrom

Now, we have a better way of testing the API availability;
__builtin_available. The null check is replaced with the call to the
compiler-provided macro which determines if the code is running in a
version of OS where the API is known to exist.

Also, this change removes __ANDROID_API__ guards in favor of
__INTRODUCED_IN macros.

Bug: 150860940
Bug: 134795810
Test: m

Change-Id: I78d2fdc0bf60bd8c5a82ec58884422dc534e752f