Get Thicket ready for breaking changes in Pandas 3.0

[ilumsden]

Pandas 3.0 adds several breaking changes that will almost certainly cause issues for Thicket. In particular, Pandas 3.0 removes the eager execution mode that has existed since the first release of Pandas. Instead, Pandas 3.0 will use the lazy execution mode (named "Copy-on-Write") that was introduced in version 1.5 and completed in version 2.1. For a (sort-of) full list of changes, see the in-progress changelog: https://pandas.pydata.org/pandas-docs/dev/whatsnew/v3.0.0.html

This PR is for tracking progress on supporting Pandas 3.0

[github-actions]

Pandas 3.0 Unit Tests Failed!

Due to breaking changes in Pandas 3.0 (namely, copy-on-write), we are performing optional
tests of Thicket against the nightly release of Pandas 3.0.

This is not a full testing failure, and it will not prevent your PR from being merged
at this time. However, as we prepare for the release of Pandas 3.0, we encourage
all developers to design their code to work with Pandas 3.0, if possible.

Pytest status code: 1
Action log: https://github.com/llnl/thicket/actions/runs/20761353693