fix: improve build logs related to plugin event handlers

[ehmicky]

This improves the headers used for plugin event handlers in the build logs:

• While those are technically build "steps", since those headers are only shown for plugins, the word "event handlers" (which is specific to plugin build steps) is more appropriate. Also, the word "step" is internal not documented, while we do use the word "event" in our documentation.
• The plugin name/location should come first, since it is more important.

[JGAntunes]

🚀 wondering if we want to tag this for docs review too?

[ehmicky]

Yes, good call 👍
cc @KyleBlankRollins

[KyleBlankRollins]

Thanks @ehmicky, this looks great! And thanks @JGAntunes for tagging me. 😄

I don't have any suggestions. You nailed it. 🔨