Add link to datasource guide for JDBC and datasource extensions

[yrodiere]

Before this patch, there are a few missing links to guides in the dev-mode landing page and in the dev UI (see below).

While I agree this patch assigns links to the same guide to multiple extensions and that's not ideal, I think it's still better than having extensions that, at first sight, would seem undocumented.

Maybe we should do the same for other extensions, such as Vert.x - HTTP?

[quarkus-bot]

Failing Jobs - Building 6daaa49

Status	Name	Step	Failures	Logs	Raw logs
✔️	JVM Tests - JDK 11
✖	JVM Tests - JDK 11 Windows	Build	Failures	Logs	Raw logs
✔️	JVM Tests - JDK 17
✖	JVM Tests - JDK 17 MacOS M1	Set up runner	⚠️ Check →	Logs	Raw logs
✔️	JVM Tests - JDK 18

Full information is available in the Build summary check run.

Failures

⚙️ JVM Tests - JDK 11 Windows #

- Failing: extensions/opentelemetry/opentelemetry/deployment 
! Skipped: integration-tests/micrometer-prometheus integration-tests/opentelemetry-vertx 

📦 extensions/opentelemetry/opentelemetry/deployment

✖ io.quarkus.opentelemetry.deployment.instrumentation.RestClientOpenTelemetryTest.client line 65 - More details - Source on GitHub

org.opentest4j.AssertionFailedError: expected: <SERVER> but was: <CLIENT>
	at org.junit.jupiter.api.AssertionFailureBuilder.build(AssertionFailureBuilder.java:151)
	at org.junit.jupiter.api.AssertionFailureBuilder.buildAndThrow(AssertionFailureBuilder.java:132)