Release candidate

• added command line option --frozen-packs
• added optimize option debug
• clean empty cprj components and group elements
• create *.cbuild.yml unconditionally when running convert
• extended *.cbuild-idx.yml with context dependencies
• extended *.cbuild-idx.yml with layer configurations
• extended *.cbuild.yml with external generator component info
• extended *.cbuild.yml with error and packs-missing node
• extended *.cbuild.yml with gpdsc project_files in group files
• fixed typos in MVE related constants
• fixed typos in default IAR linker script
• renamed selected-by to selected-by-pack
• updated schema: accept non-unique defines in *.cbuild.yml
• strip and check build metadata from pack versions
• support multiple component instances