Add Platform_sdk_version_or_codename variable

1. Added a new product variable Platform_sdk_version_or_codename;
2. This variable is used to support the logic in the Android.bp file
when either the Platform_sdk_version or the Platform_sdk_codename is
used.

Bug: 195986342
Test: m CtsThemeHostTestCases (the module where the product variable is
used)
Test: TreeHugger

Change-Id: I6b952ce47fd4adc280aa3c7ef4185487558af9bc