Deprecation warning in old tidy3d

[tylerflex]

Put deprecation warnings while importing package, suggesting users can pip install new version if they want and warning them that this version won't be updated.

[an-li-the-dev]

When user is importing lagcy tidy3d, we could check latest version by leveraging github release api,

curl \
  -H "Accept: application/vnd.github.v3+json" \
  https://api.github.com/repos/flexcompute/tidy3d/releases

[tylerflex]

tidy3d on PyPI now points to the new version so closing this.