Removed unused files in repo

There are some unused files in this repo, which may introduce unnecessary cognitive load.
I create this issue to track these files and plan to remove them one by one.
Here are the candidates:
- [ ] `snap` file: https://github.com/Azure/azure-cli/pull/27165
- [ ] `/tools`: this is an ancient version of `azdev`, but some scripts still uses it. It can be replaced with `azdev_setup.yml`
- [ ] `azure-cli2017.pyproj`: This file is used by visual studio to mark repo as Python project.
- [ ] `scripts/release/debian/Dockerfile`: not used
- [ ] `scripts/release/homebrew/pipeline.sh`: the logic is moved to `azure-pipeline.yml`, `upload.sh`: not used
- [ ] `azure/cli/command_modules/xray-0.4.2.tgz`
- [ ] `__init__.py` files: Not required in Modern PEP420. (These files also make it impossible to load `azure-xx` dependency in extensions: https://github.com/Azure/azure-cli-extensions/issues/4562#issuecomment-1780460073)
- [ ] `build_scripts/windows/scripts/setup_msi_test.ps1` and `build_scripts/windows/scripts/test_msi_package.py`
- [ ] `Dockerfile.spot` and `Dockerfile.nanoserver` #29195