This patch reorganize the files of the board inspector as follows.
1. Rename the directory name from `target` to `board_inspector`, in order to
align with the name used in ACRN documentation.
2. Move the scripts that generate the current board XML into the `legacy`
sub-directory. The legacy nodes will be removed after transitioning to the
new board XML schema completely,
3. Add the main script `cli.py` which is the command line interface of the board
inspector.
v1 -> v2:
- Rename `run.py` to `cli.py`.
Tracked-On: #5922
Signed-off-by: Junjie Mao <junjie.mao@intel.com>
