[Version] Refactor version updating logic

[comaniac]

Description

I realized that I forgot to bump the version in slapo/version.py to v0.0.2.dev0 in the last release. This results in some confusions, because when user install Slapo from source, they still see v0.0.1.dev0. This PR refactors the version updating logic to prevent this case from happening again in the future release.

1. Make slapo/version.py the only place to specify the current dev version.
2. Add a sanity check when building a wheel. Specifically, if it attempts to update the version from v0.0.x.dev0 in version.py to v0.0.y where y != x , then errors out. This is used to make sure we bump the version in version.py before releasing a new stable version.
3. Align the version when installing with setup.py.

In short, with this PR we now have the following behaviors:

1. When installing from source (e.g., pip3 install -e ".[dev]"), the version shown by pip3 show slapo would be the formal version (e.g., 0.0.2.dev13+g44aea26). Note that since we didn't change slapo/version.py, we will still see 0.0.2.dev0 if python3 -c "import slapo; print(slapo.__version__)". This is intentional.
2. Before building a wheel for release, build_wheel.sh invokes update_version.py, which modifies slapo/version.py to be the current version. Thus, the version specified in the wheel reflects the current commit. With the sanity check added in this PR, assuming we are going to release v0.0.3, before adding a tag to the repo, we require the version specified in slapo/version.py to be 0.0.3.dev0; otherwise update_version.py will error out.

Checklist

• PR's title starts with a category (e.g. [Bugfix], [Model], [Tutorial], etc)
• Changes are complete (i.e. I finished coding on this PR)
• All changes have test coverage
• Code is well-documented

cc @chhzh123

[chhzh123]

LGTM

[comaniac]

Thanks @chhzh123