Deprecate cwltool --pack in favor of cwlpack from sbpack

[mr-c]

Open --pack related issues to confirm that cwlpack fixes:

• Inconsistent behaviour in packing Inconsistent behaviour in packing  #1470
• cwltool --pack generates IDs for enum symbols cwltool --pack generates IDs for enum symbols #1513
• Behavior of cwltool --pack is inconsistent when tool has an ID Behavior of cwltool --pack is inconsistent when tool has an ID #1512
• 'main/' added when 'id' not present in workflow outputs 'main/' added when 'id' not present in workflow outputs #1436
• Not possible to pack workflow A with reference to packed workflow B Not possible to pack workflow A with reference to packed workflow B #1323
• cwltool pack creates invalid json when sub-attributes are named the same cwltool pack creates invalid json when sub-attributes are named the same #1277
• Workflow fails validation after packing Workflow fails validation after packing #1241
• Packing Error: relative path to tools are falsely handled as absolute Packing Error: relative path to tools are falsely handled as absolute #1240
• unpack a workflow unpack a workflow #1211
• '--pack' option fails when '--validate' works fine '--pack' option fails when '--validate' works fine #1103
• regression: --pack, relative run references when loading from a URL regression: --pack, relative run references when loading from a URL #1077
• cwltool --pack : field $schemas get lost cwltool --pack : field $schemas get lost #897
• Enhance --pack to replace default Files with File literals? Enhance --pack to replace default Files with File literals? #531