[SYCL] Export PI OpenCL function symbols using version script (#1638)

Export only pi* symbols in libpi_opencl.so

Changed symbols from Oclpi* to pi*
Set -fvisibility=hidden by default to hide all symbols.
version script tells only pi* symbols are global.

Cleaned up some unnecessary versioning code
Changed library scope from SHARED to MODULE to limit its usage
Moved duplicate code out of condition

Signed-off-by: Byoungro So <[email protected]>
Co-authored-by: Alexey Bader <[email protected]>

Author: bso-intel