CMake: expose Swift version through CMakeConfig.cmake (#67152)

Rationale: we are using Swift compiler as a library in a downstream project and having these exposed would streamline version detection for our use case.
Additionally, this PR makes CMake config a bit more uniform with LLVM/Clang configs.

Author: AlexDenisov

cmake/modules/SwiftConfig.cmake.in

@@ -2,6 +2,10 @@
 
 @SWIFT_CONFIG_CODE@
 
+set(SWIFT_VERSION_MAJOR @SWIFT_VERSION_MAJOR@)
+set(SWIFT_VERSION_MINOR @SWIFT_VERSION_MINOR@)
+set(SWIFT_VERSION_PATCH @SWIFT_VERSION_PATCHLEVEL@)
+
 set(SWIFT_VERSION @SWIFT_VERSION@)
 set(SWIFT_MAIN_SRC_DIR @SWIFT_SOURCE_DIR@)