Various changes for 5.26 release

[vga91]

Updated version from 5.20 to 5.26 and made changes partly similar to this 2025.x PR but with some modifications / additions.

Changes list partially from the 2025.x PR

• In RDFEndpoint.java changed @Path("/{dbname}/describe/{nodeidentifier}") to @Path("/{dbname}/describe")
  It's not possible anymore to use the endpoint as before, because it throws HTTP ERROR 400 Ambiguous URI path separator.
  This is due to neo4j 5.x uses jetty-server 10.x, as we can se here, while neo4j 2025.x uses jetty-server (see here).
  The jetty 12.x doesn't permit by default an inner endoded URL, e.g./rdf/<dbName>/describe/http%3A%2F%2Fneo4j.org%2Find%23neo4j355, like explained here for example.
  So, even if is a breaking change, that we need to change nodeidentifier from @PathParam to @QueryParam and calling it in this way /rdf/<dbName>/describe?nodeidentifier=<URI>.
  Changed the docs about it where needed.

• Changed RDFEndpointTest

  • Changed neo4j/describe/{nodeIdentifier} to neo4j/describe?nodeIdentifier=

• Changed RDFProcedureTest

  • The test multivalMultitypeSamePartialTx was flaky since it took the 1st node "Resource" that sometimes was not the correct one to be tested

• Various docs changes

  • Changed call dbms.procedures() to show procedures
  • Added appendix with the 2025.x changes

Other changes

• Various docs changes
  • Changed appendix_migration.adoc to appendix_migration_5.26-2025.x.adoc, since it affect both 5.26 and 2025.x
    • Created analogous 2025 PR: changes docs migration to include 5.26 as well #333
  • Changed dbms.unmanaged_extension_classes (deprecated) to server.unmanaged_extension_classes
    • Created analogous 2025 PR: updated docs with correct settings #332

Tests executed

Tested with neo4j 2025.06 enterprise and community.
Tested with and without apoc jars.

:POST /rdf/neo4j2/cypher
{ "cypher" : "MATCH path = (n:Order { orderID : '10785'})-[:ORDERS]->()-[:PART_OF]->(:Category { categoryName : 'Beverages'}) RETURN path " , "format": "RDF/XML" , "mappedElemsOnly" : true }

:POST http://localhost:7476/rdf/neo4j2/cypher
{ "cypher" : "MATCH path = (n:Order { orderID : '10785'})-[:ORDERS]->()-[:PART_OF]->(:Category { categoryName : 'Beverages'}) RETURN path " , "format": "RDF/XML" , "mappedElemsOnly" : true }

:GET /rdf/ping

:GET http://localhost:7476/rdf/neo4j/describe?nodeIdentifier=http%3A%2F%2Fneo4j.com%2Fmovies%2FKeanu