Refactor duplicated Rialto discovery logic into reusable CMake function

[Copilot]

Addresses code review feedback from PR #875 requesting DRY refactoring of duplicated Rialto discovery logic in test/rialtoPOC/CMakeLists.txt.

Changes

• Extracted find_and_configure_rialto() function containing Rialto dependency discovery logic (find_path, find_library, find_package_handle_standard_args, imported target creation)
• Single discovery call before defining both rialtoPOC2 and rialtoPOC3 targets instead of duplicating 40 lines per target
• Added PARENT_SCOPE to all set() calls within the function to propagate variables (RIALTO_LIBRARIES, RIALTO_INCLUDE_DIRS, RIALTO_FOUND) to parent scope

# Function to discover and configure Rialto dependencies
function(find_and_configure_rialto)
	find_path( RIALTO_INCLUDE_DIR NAMES IMediaPipeline.h PATH_SUFFIXES rialto)
	find_library( RIALTO_LIBRARY NAMES libRialtoClient.so RialtoClient )
	# ... discovery logic ...
	
	if( RIALTO_FOUND )
		set( RIALTO_LIBRARIES ${RIALTO_LIBRARY} PARENT_SCOPE )
		# ... other variables with PARENT_SCOPE ...
	endif()
endfunction()

# Call once, use for both targets
find_and_configure_rialto()

Follows existing CMake function patterns in codebase (aamp_utest_run_add, xcode_define_schema).

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.