ST6RI-927 Automatically update metamodel and version fields for standard library releases

[vytautas-astrauskas-sensmetry]

Adds a Java program called by Maven during the build that updates metamodel and version tags of the standard library as follows:

1. If sysml.metadata-tag is set in pom.xml to METAMODEL_TAG, .meta.json's metamodel field will be set to https://www.omg.org/spec/SysML/METAMODEL_TAG. For example, having <sysml.metadata-tag>20260501</sysml.metadata-tag> will result in "metamodel": "https://www.omg.org/spec/SysML/20260501". Similarly, for KerML.

2. If sysml.build-tag is set in pom.xml to BUILD_TAG, version and versionConstraint fields will get -dev.BUILD_TAG suffix and resource IRI will have its date updated to BUILD_TAG. For example, having <sysml.build-tag>20260501</sysml.build-tag> will result in the following:

   "version": "2.1.0-dev.20260501",
   "usage": [
     {
       "resource": "https://www.omg.org/spec/KerML/20260501/Semantic-Library.kpar",
       "versionConstraint": "1.1.0-dev.20260501"
     },
   

Currently, both tags are set to 20260501 for the May release.

This PR also updates the version of SysML KPARs to 2.1 and the version of KerML KPARs to 1.1.

[seidewitz]

As agreed for PR #760, the METAMODEL_TAG should remain 20250201. But you can leave the BUILD_TAG as 20260501.

[seidewitz]

@vytautas-astrauskas-sensmetry
Also, please include the issue number (for this branch, ST6RI-759) in your commit messages.