Fix Vert.x Redis stable span names

[trask]

Summary

This updates Vert.x Redis stable database span names to use the generic DB span-name fallback while still excluding Redis db.namespace from span-name target selection.

In stable database semconv mode, Vert.x Redis already emits both db.namespace and server.address / server.port. Redis semconv says the Redis database index (db.namespace) should not be used in span names, so stable span names should fall through to the available server target, e.g. GET localhost:6379, instead of remaining command-only or using the DB index.

Default / old database semconv span names remain command-only.

[Copilot]

Pull request overview

This PR updates Vert.x Redis client instrumentation to produce stable database span names using the generic DB span-name fallback logic, while intentionally excluding Redis db.namespace (database index) from span-name target selection. This aligns Redis span naming with stable DB semantic conventions: prefer {db.operation.name} {server.address:server.port} over including the DB index.

Changes:

• Switch span naming from a command-only extractor to DbClientSpanNameExtractor, using a specialized attributes getter that returns null for db.namespace so span-name target falls back to server.address:server.port.
• Keep emitting db.namespace as an attribute in stable semconv mode (only excluding it from the span-name target selection).
• Update Vert.x Redis client tests to assert the new stable semconv span names (e.g., GET localhost:6379) while preserving old-semconv command-only names.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
instrumentation/vertx/vertx-redis-client-4.0/javaagent/src/test/java/io/opentelemetry/javaagent/instrumentation/vertx/redisclient/v4_0/VertxRedisClientTest.java	Updates span name assertions to expect {OP} {host}:{port} in stable DB semconv mode and command-only names otherwise.
instrumentation/vertx/vertx-redis-client-4.0/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/vertx/redisclient/v4_0/VertxRedisClientSingletons.java	Uses DbClientSpanNameExtractor with a span-name attributes getter that suppresses db.namespace so naming falls back to server target.
instrumentation/vertx/vertx-redis-client-4.0/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/vertx/redisclient/v4_0/VertxRedisClientAttributesGetter.java	Makes the getter non-final to allow the span-name-specific anonymous override of getDbNamespace.

[laurit]

since we are going to need this in multiple instrumentations an alternative could be a wrapper for DbClientAttributesGetter that delegates other methods, but not getDbNamespace