`BUNDLE_SYMBOLIC_NAME` is `BUILD_TYPE` independent

[PengZheng]

Unlike BUNDLE_FILE and BUNDLE_FILENAME, BUNDLE_SYMBOLIC_NAME is independent of BUILD_TYPE. Therefore:

• It should be set in build-type independent targets file CelixTargets.cmake rather than CelixTargets-*.cmake
• There is no need to use _celix_extract_imported_bundle_info to get it from an imported target.