Site goal seems to need some something from the build lifecycle phase

### Affected version

3.21.0

### Bug description

From https://github.com/apache/maven-jxr/pull/342:

The JXR-plugin is a project with subprojects (parent, jxr and jxr-plugin). The `site` goal (and therefor the GH action) fails for it, as the report can not find project own dependencies. It only works if you run `verify` together with it

This means `mvn clean site` fails. But if you run `mvn clean verify site` it works as then the project own dependencies are created and existing in the project directory (or reactor?). So it seems that the `site` goal of the site-plugin depends on the verify page, but does enforce it. Other plugins, e.g. the PMD-plugin, enforces it by forking and running a verify every time the rendering goal is executed.

The [site`goal's page](https://maven.apache.org/plugins/maven-site-plugin/site-mojo.html) mentions it relies on `test` phase dependency resolution: "Requires dependency resolution of artifacts in scope: test".

Reproduce the reported difference between `mvn clean site` and `mvn clean verify site` using the JXR multi-module project described in the issue. Read the site goal documentation, including its test-scope dependency-resolution requirement, and compare the PMD plugin's rendering behavior. Done means the site goal reliably handles project-owned dependencies without requiring a separate verify invocation.

Written by the indexing model from the issue text.