Fix external javadoc reference to server project (#59000) (#59117)

* Fix external javadoc reference to server project

This fixes https://github.com/elastic/infra/issues/20103
The problem here is that we rename all artifacts in the :server project to
elasticsearch. The ideal fix would be to rename the gradle project there
to elasticsearch. I'm open to that but it seems quite invasive. Would love to hear
other opinions on that.
The applied alternative minimal invasive fix provided with this PR just takes
potential renamed projects / artifacts (Currently I only see `:server`) into account
when declaring external links.

* Simplify javadoc link base name

build.gradle

@@ -259,7 +259,8 @@ allprojects {
         } else {
           // Link to non-shadowed dependant projects
           project.javadoc.dependsOn "${upstreamProject.path}:javadoc"
-          String artifactPath = dep.group.replaceAll('\\.', '/') + '/' + dep.name.replaceAll('\\.', '/') + '/' + dep.version
+          String externalLinkName = upstreamProject.archivesBaseName
+          String artifactPath = dep.group.replaceAll('\\.', '/') + '/' + externalLinkName.replaceAll('\\.', '/') + '/' + dep.version
           project.javadoc.options.linksOffline artifactsHost + "/javadoc/" + artifactPath, "${upstreamProject.buildDir}/docs/javadoc/"
         }
       }