Resolve dirNameRoutePrefix interferes with auto-hooks

[MrWook]

Should resolve #453

Previously the prefix from dirNameRoutePrefix was used as a key to build the plugins which resulted in an unexpected behaviour.
For example with:

fastify.register(pluginAutoload, {
  autoHooks: true,
  cascadeHooks: true,
  // ISSUE: The parent folder routes and the first-level child routes will inherit the last registered hook (e.g., third.hook.mjs).
  dirNameRoutePrefix: false,
})

The routes in the parent folder were using the child folder hooks and if you have multiple child folder in the parent folder all of them would be using the last registered hook see the issue.

I tested this in my reproduction repository and it seems to be working as expected now.

[jean-michelet]

Can you plz write a test that proove the bug is fixed: not having hooks registered in children plugins when dirNameRoutePrefix === false or dirNameRoutePrefix === () => false..

You can write a test here, the folder should have the name of the issue.

[MrWook]

I added tests and verified them against the previous implementation, which failed as I described earlier. These tests now effectively cover the issue.