Bump WAMR version to 2.0.0 and keep maintaining release/1.3.x until the end of 2024

[wenyongh]

Dear developers, the WAMR-1.3.2 release has been successfully created. As discussed and planned previously, we are introducing the GC (Garbage Collection) feature by merging the dev/gc_refactor branch into the main branch. Additionally, we plan to implement the memory64 feature soon. These enhancements will demand changes in the current AOT ABI, including alterations in the AOT file format, the layout of module/memory instances, the runtime APIs for AOT code and so on. Consequently, we decided to update the AOT file version from 2 to 3 and update the WAMR version to 2.0.0 for the upcoming release.

For the backward compatibility with the old AOT ABI, we have created the branch release/1.3.x. This branch will be maintained until the end of 2024, during which the critical issues will be addressed if found, while no new features will be introduced. We encourage developers to migrate to the new version to take advantage of the latest improvements and give feedbacks. Many thanks!

ps.
#3083
#3091
#2935
#2530