Update CI files:
- add another apt repository for spec test on x86-32 as some packages
cannot be downloaded with the Github default repository
- trigger the CI file when it is modified
Refactor LLVM Orc JIT to actually enable the lazy compilation and speedup
the launching process:
https://llvm.org/docs/ORCv2.html#laziness
Main modifications:
- Create LLVM module for each wasm function, wrap it with thread safe module
so that the modules can be compiled parallelly
- Lookup function from aot module instance's func_ptrs but not directly call the
function to decouple the module relationship
- Compile the function when it is first called and hasn't been compiled
- Create threads to pre-compile the WASM functions parallelly when loading
- Set Lazy JIT as default, update document and build/test scripts
Enhance workflows by caching llvm directories directly instead of
caching the llvm-xxx.tar.gz packages, so as to reduce the time
consumption of unpacking the cached LLVM packages.
Apply clang-format for core/iwasm/compilation and core/iwasm/libraries files.
Add wasm-c-api empty_imports sample to workflow test.
And enable triggering workflow when core/config.h changes.
