Support changes in InfiniTimeOrg/InfiniTime#1258
The file `lv_pinetime_theme.c` is renamed to `InfiniTimeTheme.cpp`.
Need to pick up that change in the simulator to compile with the new cpp
file if it exists.
Furthermore use the new `InfiniTimeTheme.h` header in simulator files.
Fixes: https://github.com/InfiniTimeOrg/InfiniSim/issues/49