Full implementation of changes in Amendment 82 (previously identified as Amendment 81)

[blchoy]

This is the full implementation of changes to IWXXM involved in Amendment 81 to ICAO Annex 3. It is intended for members of TT-AvData to review. Do not merge with the main branch in the wmo-im/iwxxm repository.

One can check the changes to the model at wmo-im/iwxxm-modelling#26

[blchoy]

While the proposed changes to ICAO Annex 3 by ICAO METP will be considered in the next amendment (Amendment 82) which is expected to become applicable by Nov 2025, representative of some VAACs had expressed their wish in WG-MIE/11 that they would like to commence the provision of QVACI in late 2024 even though the provided information will only be in trial status. To meet their need we will publish the schemas in Feb 2024 for public consultation and submit for Fast Track approval by mid-2025.

In view of the above, the following changes have been made to the files in the repository:

1. Updated schemas, schematron rules and examples to reflect the change of IWXXM version to 2025-2RC1, as well as the namespace to http://icao.int/iwxxm/2025-2.
2. Fixed the typo in the release note as discovered by @amilan17.

[blchoy]

I have committed some minor corrections and amendments to the model:

1. Fixed an error in the RDF file of code list 49-2/MeteorologicalFeature
2. Promoted the Stereotype of UML Class MeteorologicalFeature from type to featureType - This is to prepare for the development of IWXXM-SX. Technically it has no impact to an instance at all
3. Fixed an error in the schematron extraction script

[amilan17]

There are a couple suggestions for the release notes.

[blchoy]

@amilan17: Your suggestions checked. I have also refreshed the RDFs as requested by Jan (see #328). I think the PR is in good shape now.