[SYCL] Do not set CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS ON for plugins (#10702)
We just don't need it:
1) PI interfaces are specifically marked with __SYCL_EXPORT, e.g.
https://github.com/intel/llvm/blob/8e0cc4b7a845df9389a1313a3e680babc4d87782/sycl/include/sycl/detail/pi.h#L1148
2) We call to PI interfaces (except for `piPluginInit`) via a pointer
from a table set up during
`piPluginInit`:https://github.com/intel/llvm/blob/8e0cc4b7a845df9389a1313a3e680babc4d87782/sycl/include/sycl/detail/pi.hpp#L220
Signed-off-by: smaslov <sergey.v.maslov@intel.com>