Component <file> element changes

[ReinhardKeil]

This is a proposal for changes to https://open-cmsis-pack.github.io/Open-CMSIS-Pack-Spec/main/html/pdsc_components_pg.html#element_file

• allow select attribute also for category="header" file even if attr attribute is not template. In this case the select attribute provides a brief description of the header file. This will improve IDE selection of header where one component offers to choose from multiple independent APIs.
• unify scope attribute to just public and private for both category="header" and category="include" deprecating hidden and visible. (Note, category is not currently used by any public pack)

[jkrech]

https://github.com/Open-CMSIS-Pack/cmsis-toolbox/blob/main/docs/setup.md#extend-header-with-select Implement support as part of setup command: https://github.com/Open-CMSIS-Pack/devtools/issues/1322

Implementation is tracked here: https://github.com/Open-CMSIS-Pack/devtools/issues/1369