Builders for classical md workflows

[orionarcher]

This PR implements ElectrolyteBuilder and SolventBenchmarkBuilder classes for analysis of trajectories generated by atomate2.openmm.

The core Builder classes are supported by a variety of utility functions that interact with MDAnalysis, SolvationAnalysis, and TransportAnalysis. In addition to the usual get_items, process_items, update_targets workflow, users can also manually create an MDAnalysis.Universe directly from the taskdoc with ElectrolyteBuilder.instantiate_universe. This makes manual analysis of a small number of systems much easier.

Everything is reasonably well tested and once CI passes this will be ready for review.

NOTE: this is essentially a vastly cleaned up version of PR #1010. I linearized the commit history so that this PR is an update of PR #1087, which can be reviewed separately and merged independently of this PR.