This should allow users to use the vscode extension on ubuntu 20.04.
After https://github.com/bytecodealliance/wasm-micro-runtime/pull/2132 ,
our lldb binary for 20.04 works on ubuntu 22.04 as well.
On the other hand, lldb for 22.04 has no chance to work on ubuntu 20.04.
(because of glibc version requirement.)
Download and install the WAMR patched LLDB binary on vscode extension activation.
This allows the user to download the packaged .vsix file, where the activation script
should handle determining what LLDB binary they should use, and install it in the
correct location.
