v1.7.0: Code organizing and improvements

Changelog

• Remove the customizable PR body.
  • Now, it will always use a template body and update it according to its needs.
• Fix PR labelling. Previously, the script had issues when labelling PRs.
• Use a faster and the latest LuaCheck version from Lunarmodules/LuaRocks.
• Adjust code files in directories such as src and tools.
• Code cleanup, documenting, and organizing.