This patch makes compile milvus under windows(MSYS), including:
- some cpp adaptation for compile under msys/gcc-10.3
- install toolchain scripts for setup from MinGW/MSYS `scripts/install_deps_msys.sh`
- adaptation for POSIX API use in golang
  * using gofrs/flock instead of syscall.Flock
  * using x/exp/mmap instead of syscall.Mmap
- introducing github actions for build milvus.exe under windows/MSYS
- rocksdb's patch for MSYS
- adaptation for compile knowhere under windows
- a windows package script for pack zip file, `scripts/package_windows.sh`

issue #7706
Signed-off-by: NJi Bin <matrixji@live.com>