Update the Velocity template (Gradle)

[Strokkur424]

closes #46.

I decided to go with a few more changes than just what the issue was original for, considering similar to the Paper template, the Velocity template can be improved much further. Here's a list of all changes:

• Always use Kotlin DSL for Gradle build scripts.
• Automatically use latest Gradle version.
• Dynamically resolve all Gradle plugin and Velocity API versions.
• Add support for the new Gradle plugin option types.
• Use Java version 21 for version 3.5.0 and above (new requirement).
• Introduce support for using the version catalog.
• Add the option to manually use velocity-plugin.json instead of the annotation processor.
• Add option to use jpenilla's resource-factory Velocity convention Gradle plugin.
• Add support for the run-velocity Gradle plugin.
• Allow explicitly choosing whether to use build constants templating.
• General minor improvements to the template files.

TODO:

• Verify that Maven project creation has not been altered/fix it if needed.
• Add missing translations.